when it was new it could absolutely tow 5k. and that's with a stock radiator with an e-fan added. but after 30 years the brake system is now, well, 30 years old so I'd focus on making sure it's up to snuff. most if not all states require trailer brakes at a certain point, usually around 3k#.
only an MJ hitch will bolt to an MJ so once you get one, all will become obvious as to how it mounts. (basically it mounts using the frame mounts of the bumper)