I have done so far window tint for the front windows and HID aftermarket low beams and I am going to be doing the DIC upgrade when I get back from my holidays in Oct and I am also doing a steering wheel upgrade to a leather wrapped wheel with radio controls.
Have you installed the steering wheel yet? I have tried what you are thinking of doing and I could not get it to work. I purchased a leather wrapped steering wheel off of ebay from an Enclave. All the wiring hooked up correctly and the stereo buttons illuminated but they would not control the radio. I tested all of the switches with a multi-meter and they all checked out. The cruise buttons all worked fine but not the radio ones. I am really curious what you find out.