That AMC straight six is one of the better American engines. Its pretty common for owners to get at least 200,000 miles out of them, plus they're easy to maintain and parts are affordable. As with any Jeep, there is a chance that suspension parts have been modified or replaced. Its common for Jeepers to add skid plates, replace shocks, axles, gears, control arms and, of course, wheels and tires. Some modifications will make the rig more trail friendly and make it less highway friendly. If you do a lot of highway driving...big tires and re-gearing can have less than desirable effect on gas mileage.
Check out the Cherokee forums at
www.jeepsunlimited.com and see what people are talking about.
I had a '94 with relatively low miles. I replaced a radiator, two starters and the aforementioned crankshaft position sensor. Look at the wikipedia entry on Cherokee. Its basically the grandfather of all unibody SUVs on the market today.