1999 Jeep Cherokee A/C compressor replacement

Keeping in mind, if there is any freon left in the system, by law you are supposed to have it reclaimed. Next, if you are changing the compressor you should also change the filter/dryer. Once you have the compressor and dryer installed, you should have the new system "evacuated". Evacuation is holding the system under a vacuum for an hour or more. In doing this you accomplish 2 things. 1- you are checking your work for leaks if it doesn't hold vacuum and 2- it pulls any moisture you may have in the system out. Any moisture at all, even humidity will cause problems down the road. Then follow the instructions on the recharge kit, and your good to go. Hope this helps.