I have a '99 GMC Suburban with two problems. Problem #1 is no heat from the front heater. Plenty of heat from the rear heater though. I have replaced the control head and the vacuum actutor that controls the valve that supplies hot water to the heater core. The valve moves, and appears to be functioning. Problem #2 it a non-functioning horn. It is not the horn relay or the horns themselves. The problem appears to be in the switch mechanism under the driver's side air bag. How can I remove it to check it?