The compressor is the power unit of the air-conditioning system that puts the refrigerant under high pressure before it pumps it into the condenser, where it changes from a gas to a liquid.
In this case, the best move might not be a dealer at all, but an independent mechanic who can often offer more reasonable ...
Topping off a car ac system can usually put you back in the deep freeze. That's an easy DIY car repair you can do yourself ..