Sirius Radio Sir-gm1 Install In Tahoe/yukon

[2500HD 8.1]

I'm looking at installing the Sirius SIR-GM1 in my 2005 Yukon. Anyone done this install??? Is it as easy as swaping in the Sirius unit for the XM unit behind the glovebox or do you have to pull the head unit to access the wiring harness behind the unit. What's the deal with using the factory XM antenna? Do you need an adapter or just disconnect the yellow wire?

 

Any help, instructions or pictures would be greatly appreciated. I miss the Sirius that I had in my Jeep, and XM is almost not worth paying for. I heard of the rumored merger, but it does not seem like it will be approved. I want to keep the factory look and use the head unit instead of just adding a Sirius radio. Thanks.