The relays are spendy, if you try to source them separately. You can replace the entire controller for less than the price of an individual relay from GM (and it will include the relay for the GPs and intake heater). Easy replacement, too. DIY and save big $$. The controller can be had from www.gmpartsdirect.com (couldn't find the controller, but the relay is $44.24) and www.rockauto.com (RA controller part# 1R1390, $97.79).

If you must have the dealer do it, ask about the cost of replacing the entire controller vs. just a relay.