Have the refrigerant discharged by an automotive air conditioning technician. Disconnect the negative cable from the battery. If the stereo in your vehicle is equipped with an anti-theft system, make sure you have the correct activation code before disconnecting the battery. Remove the drivebelt from the compressor. Detach the electrical connector and disconnect the refrigerant lines. Unbolt the compressor and lift it from the vehicle. If a new or rebuilt compressor is being installed, follow the directions supplied with the compressor regarding the proper level of oil prior to installation. Installation is the reverse of removal. Replace any 0-rings with new ones specifically made for the type of refrigerant in your system and lubricate them with refrigerant oil, also designed specifically for your system (R-134a). Have the system evacuated, recharged and leak tested by the shop that discharged it.