If you have functional power locks - where all locks actuate at the press of the driver or passenger door lock switch - then following unit is probably in there but this needs to be confirmed. If there is a Remote Keyless Entry (RKE) receiver in your '98XJ then it would be mounted in the overhead console housing on the headliner. If you want to view/confirm that you have one in there then remove six screws that secure the housing to the bezel. I don't think you need to go to the stealership if you want to obtain/program remote transmitter fobs. The RKE receiver retains the vehicle access code(s) in non-volatile memory for as many as four transmitter fobs. To program the RKE transmitter access code into the RKE receiver requires the use of a DRB scan tool (and the proper Diagnostic Procedures manual). A good audio/remote shop should have all the required products/tools and will likely be able to set you up for much less than a dealership.

I don't know how you would know if you had keyless entry. I was lucky enough that the window sticker was still with mine, which had keyless entry listed.

I can tell you this though. You can't use a universal transmitter, and you will have to go to the Chrysler dealership to get it programmed if you buy one. I bought 2 on ebay that were listed to work with my vehicle, that did not. The ones I was sold were for a ZJ of the same year. I can post the Chrysler p/n of the key fob you'll need when I get home from work.