No problem. 4.0 auto XJ's are rated for 5ooolbs (I think). You obviously need a hitch, ball mount and ball. As far as wiring, the older XJs need a taillight adapter. I don't know if yours does or not. If you hae amber turn signals in the rear, you will need it. It adapts 3 circuts (2 signals and brake/running) down to two (signal/brake and running) for the trailer. You need to know what kind of woring the trailer has on it. It could be 7 way, 6 way or flat 4. If you don't know, install the 7 way on your rig. You can always adapt down from that. The trailer may or may not have brakes. If it does, there are two types. Electric and surge, If it has surge brakes, you won't need anything else, Surge brakes can be identified by what looks like a stacked coupler on the trailer. Should have some kind of master cylinder on it. If it has a 6 or 7 way plug, it may have electric brakes. Peek inside the wheels and see if there are drums, or look for wires coming out of the backing plate. Those require a brake controller to be mounted to your dash and wired up. If it has a flat 4 connector, it has a surge brake or no brakes, and you just need to wire for lights.
Make sense?