If your name it is a 2000XJ then the compressor is about $340 online w/a clutch. If the system is empty then its just a matter of removing the belt, unbolting the single connector on the compressor, unbolting the compressor and reversing the process. I don't know whats under that oval shaped connector, maybe O rings of some kind or a gasket, hopefully the new one will come with whatever is needed but maybe not and I would not reuse whatever is under there. Might be a good idea to replace the drying tower too. Then take it to a shop and have the system put under vacum to test, should hold vacum. This also gets the moisture out of the system. Then it needs to have pag oil added and a new charge. You for sure need to have it sucked down or it will not take any freon and the pressures will be way high. What exactly is yours doing ??