I think this adapter Audiovox XM Direct 2 Universal Car Adapter CNP2000UCA
is the XM module you need for your radio. Check the details to see that it will match your radio.
I didn't use an adapter. I used my small Sirius Sporster head unit that I move from car-to-car. That way I only pay one fee but can get Sirius in whatever I am driving.
To make an extension for the GPS coax: to avoid having to make 2 splices I spent about #30 and purchased a new GPS antenna for the radio; then I cut it about 6 feet long and used one end to plug into the radio unit plug (thus saving one splice); after cutting the end off the GPS antenna lead coming into the RV that was behind the dash I spliced the extension in. I was careful to expose as little as possible of the center conductor and tried to keep the length of the splice as short as possible. After and in-line splice on the center conductor and heat shrinking the connection I wrapped the outer braid around that splice and then put heat shrink on it too. I soldered the splices when I made them but was super careful to use as little as possible (I probably just tapped the soldering tip to the splice.).
One note, I brought the existing cable out the left side hole of the passenger side HVAC duct. The directional vent just unscrews from the duct hose. Otherwise there was no way to work on the existing antenna lead-in since it was so short.
I hope this works out for you. Let us all know how it works out.
oh - I considered using and SMA type connector for the splice but figured it was just as much trouble, if not more, than just using a splice.