How To Repair Egr Valve 2002 Saturn Sl?

I never heard of repairing an EGR valve. I always bought a new one at the parts store. It sounds like some other problem though, like the IAC or a sensor problem. May be a good idea to have a scan on the vehicle to find out if there is a code stored in the computer.

I have a 02 saturn sl2 and the check engine light is on. When its in drives the idle drops low and then stalls. I took it to autozone and they scanned my car and said it could be my gas cap not sealing right but that wouldnt make my car stall. They also said its possibly the EGR valve and he said clean it with wd40 or brake cleaner and see if that helps the idle if not then follow my valves and hoes to find the leak. Any suggestions please?