OK, more reading. Remember, you are learning to lay the groundwork to performance build your 3000GT. On the average this ends up costing most owners a MINIMUM of $5,000. And those that plan on spending $2-3000 end up spending 2-3X that more often than not. Realize that a medium high performance build covering the engine, transmission, suspension, brakes, etc. can average at around $25,000-35,000.
Seriously. It is just how it goes. (if you don't think so then start adding it up as I'll show you in this section. Those amounts are low!). SO - Read this info in it's entirety before getting to the actual parts list and money lists.

Start with basics
Tuneup/service, synthetic lubricants (oils). How's the steering system? Suspension? Body (for many owners looks does matter!). It makes no sense to start ‘mod’ing’ an engine that has worn bearings, leaky rings, etc.  That’s just silly and a failure waiting to happen. DO THE FOUNDATION FIRST.  One exception to this is if you don’t care and can afford to grenade your engine or car in general. If that’s the case go ahead and experiment with the full knowledge that you will be looking at a full rebuild sooner rather than later as well as repetitive labor.

CLICK HERE to open a window that lists what I consider a proper 60,000 miles service and tuneup.
A typical price for a THOROUGH 60K is around $1,800-2,700 on average (give or take 20% and done by competent experience mechanics). It is much more than an oil change and timing belt.
The 60K page at that link gives the info on basic maintenance and also some tips on parts acquisition.

Remember when budgeting – things like gaskets, bolts, wiring, etc. can all ADD UP! So you must factor this into the build cost. You cannot just go with the cost of the major components. Many times the cost of the supporting incidentals can be more than the main part you want to add! A PROPER budget is a very important thing to compile if you want to have the most success and the least failure or grief.

A little introspection is very helpful at this point. Meaning – what do you want to do to your car? And let’s be realistic here. Leave the dreams in your bedroom for right now. Don’t say you want 600AWHP and you have $2000 to spend. That’s just not going to happen. It borders on the foolish.

So choose:

Fix up my car a little but retain reliability. The RELIABILITY is an important factor to consider. The MORE your modify for performance (ie – HP mostly) the more you lose reliability and longevity. It is just a fact of life. The more you push your turbocharged V6 the sooner things will fail or quit working properly. If you want to RETAIN the reliability and longevity then admit this in the beginning and stay away from the higher modifications. Stick with the basic bolt on modifications that just increase your engines’ efficiency (like a nice downpipe for example, or air filtration system).

From here you can go into several different levels. Up to you to decide what you want (and realistically afford!). 

Another factor to consider here is what can you absorb as acceptable losses? Performance building is full of things that go wrong and cost 2, 3, 4X what you planned on. It is normal in the world of performance car building. So what can you accept financially if you damage your engine. If you cannot afford to rebuild your engine then don’t plan on a 600+ HP upper stage build.  I’m not saying that it will happen but you have to realize that by stepping up into those ranges you increase the likelihood of that happening by about 10 fold. It’s just the nature of the game in high HP setups.

Figure Out Your Goal.

At least get some idea of what you want to do. The more accurate you can nail this down the easier things will be in the future decision requirements later. Sometimes goals change and that is okay (to a point) but you must have a direction. Your goal is going to dictate some what major components like turbos as well as supporting them like injectors and engine management control.

Budget

Can you afford what your goal is. If they do not match up then you have to either adjust your goal or adjust your budget. Let’s get them to match to a reasonable degree before going forward. That will save a lot of time and wasted purchases. Don't just count on the main components. You MUST count on all the parts or your budget will be all skewed. You will either run out of money (and have a table with lots of parts laying on it), have to change your whole plan (and possible sell, at a loss, some of those parts), or find the extra money you did not have available or want to spend in the beginning.

Those are the two most important things above. Many don’t do this properly. Amazing when you think that in the end some of these people are about to spend over half or more of what they earn a year into their car!

I would suggest using a spreadsheet (ie – Microsoft Excel) to layout your build.
Well, if you are just doing some simple bolt on mods that’s probably not needed. But if you are one of those that wants that “400-500 AWHP” and have a budget of $10,000 or more then I would seriously recommend using a spreadsheet.  In fact I use a sample spreadsheet of my 3000GT race car to show how a budget can climb to over $150,000 very fast. (My Racecar Sample Beginning Spreadsheet from 2008). The sample spreadsheet shows some basic numbers that are pretty accurate in the building phases. I've done all the things on that old spreadsheet and a few changes or additions since then. So it is an accurate depiction or real life building. Even if you aren't building a race car the sheet will give you a brief idea of budgeting and how it adds up fast. Feel free to copy it and use it for your own build by deleting and/or adding your own.

Anytime I start to spec a build the first step is setting some basic goals and budget requirements.

Then it is time to open excel and get a spreadsheet going. This is the only way to run a larger scale build and know what things will cost you. You can also plug in the factors to help you see if your goal is matching your budget. They usually don't match up well at first and one or the other has to be changed.

A quick note about buying used electronics - be careful. With electronics or anything else that cannot be verified easily with your eyes or simple operation or testing. You usually cannot get your money back on bad electronics if it wasn't bought brand new. The problem with many used car parts like electronics is that they are not 100% dead or non-functional. But many times they have something wrong and is why it's being sold off. You can end up chasing gremlins and ghosts all over for days or weeks because of it. So watch out for the really good deals or 'saving a lot of money'. There's nothing wrong with saving money but not if it costs you 10X the labor and time or replacement parts to find these gremlins they cause! And by the time you figure it out (if you do) the seller is long gone.

MY ADVICE IS TO BUY CRITICAL ELECTRONICS NEW ONLY.
Critical means that if they fail or have a problem your engine will not run properly or can cause damage if they fail or do not function as designed. By buying new you have a much better assurance of the product performing properly as well as the manufacturer warranty.

A NOTE ABOUT OEM SYSTEM REMOVALS

This is another thing related to things people read on the internet. People that talk about the removal of OEM systems or engineered items. Things like ABS removal, EGR removal, crash bar removal, vacuum reduction, EVAP removal, AWS removal, harmonic balancer removal, etc. 99% of the time this is NOT a good idea for the individual. While there are some very specific applications where it can be useful, for the average and street car it is not. It is right up there with converting an SL or base to a turbo (which we already addressed as a terrible idea and why).

Remember that the manufacturer spent a huge amount of money engineering and putting into production those parts for the system. Over the entire design of the car this can approach millions of dollars. Realize that they do not do that lightly (or they would go broke from mismanagement, lol) so they had VERY good reasons to do it a certain way. Yes yes I know, some will come up with some instances on certain things where it MIGHT be a good idea. Just realize that MOST OF THE TIME you are not gaining anything for your money and labor and worst case you are actually losing performance or even introducing a safety hazard (like removal of the front crash bar - never ever do this!).

So my advice is to the average builder is to leave your ABS system alone, leave your EGR system intact, never ever remove your crash bar (even my dedicated drag car has a front crash bar!), do not mess with your evap system (can cause serious gas fume problems and safety issues), AWS is awesome but if you don't think so then removal will not gain much except some weight savings, leave the factory balancer on your engine because it serves a very important purpose as most all engine builders have known for a very long time. Do not remove things like radiator shrouds, or stupid things like put fans on your SMIC, or replace breather lines with silicone hoses (the are not oil compatible), sigh, the list goes on but you get the idea.

Let's go on to the actual build list now.