Have it checked thoroughly by your mechanic before you buy it, at around $40 it will be the best insurance policy against a problematic vehicle..and these can have thier problems.
GC's -and all other Jeeps with the 4.0L- will experience blow by in the engine as early as 50K miles, despite an improved setup within the oil control and PCV systems installed by '97. Ball joints are another big issue on GC's. Before long you will see oil in the vacum/PCV lines and hoses as well as signs of oil in the air filter housing in sever cases. I'm a former Jeep tech, and still service a number of them at the shop I work at today and I'm still seeing the same issues witht he 4.0L. I love the motor in Wranglers but not in the GC, that should have an 8cyl.
Oil leaks in the valve cover, and more serious leaks at the rear main seal are also very common, along with leaks in the transfer case cover gaskets and shaft seal.
That's all I can think of right now, but it's late