I also agree with Ian. The 2001 head issue is apparently hit-or-miss, I guess it would depend on if it's ever been overheated in its lifetime. My '01 Cherokee has the same motor, and hasn't had any issues (has 80K on it now). However, one of the guys I work with also has an '01 Cherokee and the head cracked on his at 60K miles; his was overheated in the past.
FWIW, My mom had a '99 GC with the 4.0 and it was very reliable. It did have some electrical issues; I had to replace a front window regulator and a rear door lock solenoid, and before she traded it in, there were some large wet spots in the rear cargo area. I think the seal around the rear side window failed and water was getting in during heavy rain. My brother-in-law has an '04 GC and it's been relatively problem free nearing 70K miles. And, he beats the death out of it.
Cliff's Notes - Jeeps FTW!!!
