everything...start with belts, hoses and lights. Suspension and so on...When I drove from MA to LA that was 1500 one way. I had a 91 XJ with 200K on it. I changed all fluids, brakes were due anyways, did those. I brought an extra drive belt, and water. I had done the hubs a few months eailer so I knew them were good. Tie rods, ball joints the whole front end make sure it's tight, check your tires for nails and screws...Long trips in Jeeps are fun!