I'm on my second GC. I bought a 93 new and then traded it in on a new 2000. My experience is that the gizmos have a tendency to go bad because of wiring problems. I had to replace the automatic antenna (warranty) and had to fix broken wires in the harness going to the drivers door. I also had problems with the battery cable a couple of times. I put about 80,000 miles on the 93 and never had to do anything major. I did replace the transmission skid plate after a particularly fun weekend in Moab. Overall my experience has been very good. I have had the 2000 for almost 3 years. I had to have the front rotors turned because of the infamous rotor warp problem. Other than that, no problems.
Things to look out for are:
AC leaks - compressor failures
Transmission - rough shifting
Check fluids to make sure they have been changed on schedule.
All windows and locks working
The normal stuff you would check on any used car.
If the engines are maintained you should get between 150,000 and 200,000 miles out of them.
Get the V8 if you plan on towing anything or just want a really quick jeep. The gas milage is about the same for both the 6 and 8 cylinder engines.
Happy shopping. They are loads of fun.