Welcome to NICO.....
First order of business is to know when the timing belt was done. I think the 93 and 94s had 60k service intervals, and the 95+ had 100k service intervals.. regardless, if the car has over 100k on the clock, it should have had the timing belt replaced at least once, maybe twice...
The timing belt job usually costs about 1000 out the door at the dealer, they replace the water pump, cam seals and a bunch of other crap....
http://www.fuzzycats.com/j30.htm - Check out this website for starters, one of our members, Carlos, made this little resource for the J.. pretty good resource..
Other than that, youll want ot add an external transmission cooler.. Fortunately they use the same transmission as the Z32, so the Z guys are always wiling to give those things away for barely anything!
One final thing... You need to make sure there are some service records... Im very spoiled in that I can call up the previous owner of my Q and ask him when he did certain things... The more complete the better, however if they are kinda patchy, a LOT can be told by the condition of the fluids... The tranyn fluid and PS fluid should both be kind of like the color of blood, except more pink... If you look under the oil filler cap and down into the hole, it should be fairly clean (you should see metal), may have a slight little film on it but it shoudl wipe clean to reveal fresh metal.. Anything caked on, brown or black, and run as fast as you can away from it!
If, and ONLY if all that stuff from above checks out, id take it to a decent mechanic to have it inspected, or maybe you can get one of our NICO guys to come look at it. Some shops will let you use their lift for a few dollars if theyre not busy...
$100 paid in an inspection could save you THOUSANDS later!!!!