I bought my Jeep in 2003 as a used vehicle. It had 75,000 miles on it which is a lot for only being 3 years old. Since I've had it nothing major has gone wrong with the exception of the right front brake caliper locking against the rotor. Everything that has gone wrong with it before that happened when it was still under warranty.
4.0 I6 motor is probably the best motor Jeep has ever offered...it's nearly bullet proof if you take care of it.
Not much you can do about it now. But if something had to be changed it would be the size of the stock tires. the 225/75/R15's are just too small to do any minor off-roading.