I have a 95 Nissan Quest which has given us good service for a number of years. Recently the a/c quit blowing cool air and I had the Shraeder valve replaced. The mechanic noticed that the a/c cooler was damaged by rocks coming up and putting dents and causing a small leak. He did not recommend putting a sealer in the system as he said it would gum up the system. Does anyone know how difficult it is to change out the cooler as a do-it-yourself project. I can have the repair shop empty the system and then change out the cooler myself and have them re-charge the system. Any help would be appreciated.