I just bought an 05 Chevy CrewCab with Onstar and the Bose system, but no XM. I'd like to add XM to the factory radio. I found a kit to add it, GM PN 12498768. I also learned that you can use a combined antenna so that you only have one on your roof instead of two. That's GM 15194280 for the antenna and GM 15292901 for the wiring harness to hook it all up. My question is: Is this the way it would have come from the factory? In other words, would there be any difference between my truck and one that rolled off the line with it?

Anything else I should know before I make the modification?

Thanks!