Cost Estimate For 2003 Camry AC Repair

My 2003 Toyota Camry air conditioning works for 20 minutes and then starts blowing hot air. I took my car to the Toyota service department and they said I needed to replace the relay of the air conditioning clutch to the compressor. The technician quoted me a cost of $531 to replace the relay however they said it may need repairs in addition to the relay. Right now they can't tell if it needs additional repairs because the technician said that the ac doesn't run long enough to be able to tell. My question is should I allow them to replace the relay for $531.00 even though they are saying that may not be enough to repair the problem. Please advise on whether I need to get a second opinion?

Thanks.

This may be something totally unrelated but since the dealer mentioned relay, is your A/C light blinking when it starts to blow warm air? If so, read this thread from another forum.

http://www.toyotanation.com/forum/104-camry-5th-6th-gen-2002-2006-2007-2011-2nd-gen-solara-2004-2008/407784-toyota-camry-c-button-flashing-blinking-repair-13-99-instead-1200-a.html

Mike