If you haven't already discovered it, the website
Turbo Regal Web Site has LOTS of invaluable information. When I first got my GN I spent days on end reading everything on that site. Specifically for you, it'd be worthwhile to perform their basic "
The Grand National / T-Type / Turbo Regal Buick Spring Cleaning Guide" checklist. That gives you a good base to start messin around with your car. Before you do any of that (messing around with the car that is) I agree STRONGLY with the previous posts... the stock boost and tach gauges are pretty much worthless, some of your first purchases for the car should be a decent set of gauges. If money is an issue, you can probably pick up some good used ones on this site in the parts for sale section. I got a set of used boost, oil pressure, knock, and water temp gauges, as well as pods to mount them on the A-pillar (boost and knock) and in the console (other two) all from guys on this site, and for a pretty good price. It would also be a good idea to get a scantool of some kind. This will enable you to monitor (and depending on what you get) record all the information your ECM is sending/recieving. Its an invaluable tool for diagnosing problems and tuning your car. As far as which scantool to get, there are several to chose from. Some basic standalone ones (the classic scanmaster) to much more detailed laptop based programs. They vary in expense, scan rate (how many times a second they sample the data stream), and other features (some have ability to record data for a period of time which allows you to share that with experts on this board who can then diagnose your problems). Do some research before you buy, as they can be expensive.
Lastly, almost any question you can think of has probably been asked and answered several times on here. You can save yourself a LOT of time by using the advanced search feature. It may take a few minutes of trying different search options and keywords, but you can almost always find your answer. I'm not trying to discourage you from posting new threads, thats what the board is here for. I just can't tell you how many times I've gotten on here to ask something and found it by searching in 5 minutes, which saves a lot of time compared to waiting for people to read and respond to your post.
Congrats on being one of the select few to own a piece of American history... ENJOY IT!