one thing I have seen in shops I've worked in about the 4.0 water pump- You have to be sure the correct one is being installed. Ealier years has a regular V-belt. Those pumps will fit your 4.0 serpentine belted motor but will spin in the opposite direction causing overheating. The store should be able to re-check the part number. Also I usually bleed air from these while filling the cooling system by pulling the heater hose slightly off the thermostat housing. When coolant comes out there, reinstall it.
96 GC Limited V8 245,000 miles Scrapped
04 GC Limited 4.0 264,000 miles
96 GC 4.0 175,000