Aux Input through Factory XM

Hi folks!

I'd like to use the audio output lines from my XM factory unit to create an aux input. I figured I would have a relay or mechanical switch to switch between the XM and aux signals. Does anyone know the pin-outs of the XM radio plug which ends up going into the MFD? I haven't been able to find anything of the sort in the forums. Maybe if someone has the MFD pin-outs, I could trace back from there.

Thanks for your help!