if i could do it all over again id go private.
Old car > parts wear, dealers import them and flog them to prospective buyers asap with out replacing items.
Private owner would have replaced worn suspesion, fresh service, tires, brakes etc.. Im not saying dealer's don't replace items they just do it on a budget...
Plenty of tidy units out there for sale, with low demand you will surely get a steal if you shop around. Id budget 25-30k
Check for rust
4th Synchro is known for it's laziness, and 3rd pops easy.
Warped rotors
Definately spend the few hundred to get it checked by a mechanic and try buy one which has had some work done... the 4-5k which you pay over a stock GTR will get you one with all the needed work done, saving you $$,$$$$ later down the track.
Cheers Tomek