Buick Rendezvous Idle Air Control

I'm Trying To Help A Friend Who Recently Got Screwed Over By A Very Expensive "mechanic". The Main Problem He's Having Is...

Where Is The Idle Control Valve Located In 2004 Buick Rendezvous? Also If This Has Gone Out, Is It Safe For Me To Drive On The Highway?

My 2003 Buick Rendezvous At Times Will Drive Up To 50mph Without Even Touching The Gas Pedal. Any Suggestions? I Have Replaced The Idle...