WARNING: This page is about a different car, the 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Nut Attaching The Foot Rest To Side Rail & Dash Panel Stud
Courtesy of GENERAL MOTORS CORP.
Remove the nut attaching the foot rest to the side rail.
Remove the nut attaching the foot rest to the dash panel stud.