My parents have the same vehicle (98 5.9 zj limited) that they bought when it was a year old and still have it. Does the a/c and heat work? It seems like they have problems with the blend doors, ac, etc. My parents has close to 200k on it now and is having quite a few electrical gremlins, but still runs and drives fine.
Sounds like a nice jeep, but 4k seems pretty steep with that many miles. It may be worth it if it's really nice and you can get him down closer to 3k.
I would suggest doing research in the zj area.
2001 amber fire cherokee sport 4x4, 2 in lift, 30x9.50 generals, 174 ion wheels, pretty much stock.