I purchased a used 2010 Traverse. I was surprised that it did not have XM already since it is a standard option. I found the original sticker from the dealership in the car and it shows a delete option on both the XM and Onstar. Can I purchase just the XM module and add it? What I read said as long as the stereo had the CAT button it supports XM but I'm just not totally sure about the antenna and all? Any ideas? I found a used XM module from a junk yard from a totalled Traverse and they only want like $60 for it.