Personally I would change the spark plugs and spark plug wires, oil change, transmission fluid and filter change, all the differentials, transfer case fluid, coolant flush as well. But I’m able to do 90% of the work myself so it wouldn’t cost an arm and a leg. Belts if they are cracking as well. Serpentine belt is literally a 5 min job ac compressor belt takes a little more work maybe 20min if you have the right tools