You need to replace the receiver / drier , which is the cylinder located by the alternator with the sight glass on top of the cylinder . You also need to replace the expansion valve which is the block located where the 2 AC hoses connect at the firewall .Buy some AC flush before putting the new parts on and pour the flush in the rest of the AC system , follow the directions as to how long to leave the flush in then blow it out with an air gun . As far as the new compressor goes it will have a small amount of oil in it but not enough for the entire system and you or the AC shop will have to add more . When replacing all the orings make sure you coat the orings with the PAG oil ( refrigerant oil ) . The AC shop will run a vacuum test to make sure it does not have a leak before filling with refrigerant and PAG oil.