You are going to have to have an a/c recovery machine to evacuate, vacuum and recharge the a/c syst\em. You have to remove the whole instrument panel and lay across the seats, and then remove the heater box. You will disassemble the bos to get to the evaporator. Reassemble, vacuum the system and recharge it. If you want to do it yourself and don't have access to an a/c machine you could go to a shop or dealer and have them evacuate it and recharge it after you are done with the repair. I enclosed the instructions. This is a very big job for alot of do-it-yourselfers. It would be best if you bought a manual for it before you started. Good luck, and if you run into any problems or need anything else let me know.
Recover the refrigerant from the refrigerant system. Remove the front expansion valve from the evaporator tube mounting flange. Disconnect the heater hoses from the heater core tubes. Remove the four nuts from the heater-A/C housing mounting studs on the engine compartment side of the dash panel Disengage the front floor panel transmission tunnel duct from the adapter on the heater-A/C housing. Remove the nut that secures the heater-A/C housing mounting brace to the stud on the passenger compartment side of the dash panel. Pull the heater-A/C housing rearward far enough for the mounting studs and the evaporator condensate drain tube to clear the dash panel holes. Remove the heater-A/C housing from the vehicle.
Disassemble the heater box and replace evaporator.