Check for rust under the car, inside the fenders, around the gas-cap, and in the rear strut tower areas (have to pull the carpet out of the way)
Check to see if the lower intake manifold has been replaced with the aluminum ones (if the Grand Prix is 2003 or older)
Beat the piss out of it test driving it and make sure everything feels good, and the transmission is solid.
For $6300, you can afford anything from 97-07, except for a nice condition GXP (5.3L v8)
Best bet would to be to decide between the 97-03 body style, or the 04-08 Bodystyle and go from there. Obviously the newer the car, the better shape it SHOULD be in. But there are always exceptions to the rule.
You can get a good 97-03 for under $4000, and have money left over to repair anything it needs, and put a few mods into it. That's what I did.
Or if Blue hasn't sold his yet, buy that sexy thing.
