As for the Sony unit, its been disconnected for over a year. I think I threw it in the trash so that nobody else would have to put up with it. I agree it was a terrible unit.
I am lucky that I did not have to pay for it though. I work for GM (who I believe owns 20% of XM). GM had an employee deal where the Sony hardware was free with a 6-month commitment to XM. I took the deal, had the service for aobut 8 months and disconnected it due to the poor sound quality. The antenna stayed in the vehicle since it was easy to leave it there. All the wiring was hidden behind trim panels.
I gave the vehicle to my dad, he wanted XM so we got him the SkyFi unit, and thus I had the Sony antenna with the SkyFi receiver. I'm very grateful for your advice, as I know little about antennas and did not want to risk destroying the SkyFi antenna wiring in a failed attempt to adapt it to the Sony antenna. I was about to begin the long process of removing the one antenna and replacing it with the other (which would have required removing a lot of trim panels), but then I decided to throw the question out here on AVS. Thank goodness for this forum and your reply.