Clean out the entire throttle body. The carbon buildup that accumulates in the IAC trac can be part of the problem. Also make sure there are no loose or cracked vacuum lines. Lastly make sure the TPS sensor is properly set. These are all things that can screw with your idle.

PS: Never buy stuff from a dealer unless you absolutely have to. IAC valve can be have for $50 or less on Clublexus/Ebay/etc.