Sounds like a solid decision. Don't be discouraged. Keep doing research. Look at the cars for sale section on this board and see how members present their car. Look at the questions people ask about it. Literally write down a list of questions that you see become common. Use that list for other ads you find. Start to monitor the market so you get an idea of what prices are associated with what level of quality.
You can do a search on ebay of COMPLETED auctions. compare what those cars offered condition wise compared to their asking price. Look at the ones that actually sold and their final sales price. Get some idea of what prices cars are NOT going to sell at and go from there. No two GN's are the same, so it is going to be a grey area when it comes to valuation. That is why it is important to identify what you want.
You will find cars that are pampered trailer queens, cars that are pavement pounding speed demons, cars that are in between, and cars that had their owners fail them, resulting in a messy heartbreak. As others have said, the hunt is actually pretty fun and it helps keep the dream alive, especially if you are saving money to buy a better one. Watch out for Wife aggro. She will need to be on board with this car. Involve her in your dream, and let her know it is important to you to achieve it. Remember these care are almost 30years old. Even a pristine condition car is going to need a little more attention than your daily driver. Replacement parts can get expensive for these cars. (Search the site for Powermaster). She needs to be prepared for that. I encourage you to keep an eye on the general tech forums to see what kind of issues folks have and how they resolve them.
Don't limit yourself by thinking 'only local'. Getting a familiarity with what's out there and how much folks want for them is essential in evaluating the value in what you have found. I will offer that in my observations that in the past two years April/May the biggest selection of cars were available, but all had higher prices (When warm weather hits is usually when folks get the itch for a toy so higher demand). September/October owners were most open to negotiating price if they lived in a snowfall region. (They want to avoid putting the car in storage again).
I may get flamed for saying this, but I am of the opinion you should NOT buy one of these cars from a dealer. Not unless you know who the previous owner was. They all have the same story of a little old lady who got the car from he deceased husband and it just sat in the garage. Remember, our cars only have 5 digit odometers. Once it crosses 99,999, you get to have a 'low milage' car again. I have seen dealers detail the hell out of cars and pass them off as barn finds. Sure I suppose a private owner could do the same thing, but generally speaking when you find an owner that was passionate about these cars, you can tell it because he loves to talk about the car. Lots of stories he will have. . Salesmen are always enthusiastic. in my experience. (no offense to anyone).
I hope this opinion helps you in your search. These cars drive like no other, and are addicting, but can seem like they are a vacuum cleaner to your bank account if you get one at the wrong stage of its life. I didn't believe people when they told this to me in during my search, but if you can be patient, and look at lots of cars, you will 'know' when you have found the car you were looking for.
Good Luck!