If you have no history of maintenance, change out ALL fluids. Oil, transmission fluid, transfer case, both differentials, coolant (replace with factory 195 OEM thermostat while you're doing this). Fluids are the best investment on future reliability of your XJ.
For tuneup hardware, you'd be looking at replacing spark plugs, plug wires, distributor cap, rotor, air filter, check belt condition.
99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!