is it possible to add radio controls to the steering wheel.

Hello, the easiest answer is to consult your local GMC dealership who can check for any accessory add on's for your Sierra 1500. My general answer is, though, that typically such items are not a "bolt on" solution. In other words, wiring, the radio itself and the software that controls everything are likely tailored to the individual vehicle, and cannot be modified. Still, do check with your local dealership as in this case, they are the definite experts and reliable source. Good luck!