1991 C2 air conditioner condenser

Vehicle Information: Year: 1991; Body Type: Coupe; Total Mileage: 91,000;

My air conditioner has stopped working. It was re-charged last September and is no longer cooling. The mechanic cannot find a leak and is therefore assuming it is the problem is the condenser. I was told that it would be really expensive to replace the condenser (the parts would be over $700) and the labor alone (removal of the dashboard) would be in excess of $1,000. I spoke to another mechanic on the phone who said there might be extensive damage from 'grenading' which could have sent particulants all over the system. I am at a loss as to what to do. Do you have any advice?