Sounds like you could use some help. You can ask questions on the board and wait for a response but.....
If you are thinking of a bike, hopefully you have friends that already ride and can help you out. Especially if they have some kind of mechanic background. An older rider can give you some tips on the vintage bikes. I'll offer you some advice here though.
I have had many bikes over the years and have bought a vintage bike as recently as a year or so ago. The early gixxers were oil/air cooled and in my opinion not as trustworthy if they have high miles. I owned a 1986 750. But they can still be a good bike.
I know this is going to sound hypocritical, but when I hunt for an older bike, the two most important things are that it have low milage (between 10K and 25K if possible) and that it be close to stock. I know that the trick stuff like exhaust, etc may be nice, and I almost always add some mods to my bikes, BUT to me, the more mods on a bike, the more it may be abused. I also only look at bikes with the original body and paint.
Specifically, the 88 1100 (BTW, they were 1100's up to the mid 90's) could easily be worth $2500. I would make sure it hasn't been wrecked. I also would be careful if it was safety wired (it may have been raced). If it is all original with a clean title and has low miles, I would say go for it. I would be wary of the seller since he/she told you it was a 1000, I don't much care for liars.
In the last 4 years I have bought 3 older liter size bikes. I paid less than a grand for a project bike Honda VF1000R, I paid $2700 for a 1987 Yamaha FZR1000, and $3300 for a 1992 FZR1000. Both of the Yamahas had less than 18K miles and were in excellent shape. I also want to tell you there is a BIG difference between old and new bikes. To me, the older bikes had a softer suspension and a better ride, but are slower and don't handle as well. BUT, I feel I MUST warn you, that any year liter bike is damn fast, and can compress time and space more than non-riders can imagine. I personally would not recommend a liter bike as a 1st bike unless the rider is VERY mature and has good disipline of the right wrist. Any bike can maim or kill you, but a liter bike can do it faster! Sorry to preach about this, but I think it's important if you don't know bikes. Good luck! Feel free to ask more questions if you don't mind long anwsers.