Crutchfield has them in stock ($100), got mine yesterday.
I removed my factory XM module (2004 Envoy), I hooked it up using the included antenna, activated, and it works great!
Seamless integration with the headunit. The dot-matrix display shows "SR1" and "SR2" for the bands, instead of XM1/XM2. Display of artist/song works just as with the factory XM.
Now I just need to make/buy the adapter for the factory antenna...
EDIT (I've gotten a couple of how-to emails):
More detailed install info (took me maybe 10 minutes):
I was replacing the factory XM module with the SIR-GM1, so I already had wiring to the XM module. The SIR-GM1 comes with two cables, one for installs where you are replacing XM (a 1-foot adapter cable) and one for installs without prior XM (more complicated cable that plugs into the back of the radio).
Steps for 04 Envoy:
- Remove 2 hex screws from either side of the panel under the
glovebox. The panel will drop off; the XM module is bolted to this
- Remove the antenna connector (squeeze the locking tab) and the
power/audio connector (pull out the blue locking peice, and the black
connector will pull out).
- Unbolt the XM module from the panel
- Plug the adapter cable between the factory harness and the SIR-GM1.
- Hook up the antenna (either buy/make the adapter, or use the
supplied Sirius antenna)
- Mount the unit to the plastic panel (I used 3 self tapping screws, supplied), then reinstall the panel.
I have the supplied antenna sitting on the dash until I get an adapter for the factory antenna.