Nothing is connected to the back of the head unit. The aux in jack inside the console can be purchased at the dealer. I got another one so i would not have too look at a big hole in the bottom of my cubby.
You pull off the back of the console(part with rear HVAC controls). Unplug the original aux in and connect harness to new "hidden aux in". Next plug in your mini jack ground loop isolator. Next part to plug in is a 2 into 1 mini jack,so you can run 2 sources like Ipod / MP3 / Sirius whatever .
Run the line out mini jack from the Sirius XM unit along the inside or bottom of the console to the rear and plug into one port of the mini jack 2 into 1 adapter. I then drilled a hole into the console box to run my Ipod cable. I went with one of these.
http://www.cablestogo.com/product.asp?cat_id=614&sku=35508
Sounds much better than headphone jack level out.
Dave