I and my SO installed an XM Commander into my car (a Miata), and he also installed the same receiver in his Jag. So long as you know how to cut, splice, piggyback wires, and figure out what wires do what, you should be fine.
Without going into gory detail the steps for my car were: figure out where to put antenna and receiver (the hardest part!), disconnect battery, take apart center console and middle part of dash, move aside carpet to place XM antenna, pull out needed wiring, undo previous splices (after market radio) in order to piggyback in new wires (power and FM interrupt), solder and shrink wrap new connections, slide the black box for the XM unit into the dash, put control/display unit in center console, stuff wiring into place, put car back together.
My radio is old enough that it didn’t have an aux in, which is why we ended up using the FM interrupt. Total time? About three hours or so, but we did spend some time changing all of the wires that were spliced with those twisty connectors to solder/shrink wrap connections.
The experience was similar on the Jag, with some complications because he didn’t want to cut the original wiring.
For the Miata, we only needed to pick up piggyback connectors, flux, and shrink wrap. For the Jag we needed the same and picked up some extra wiring as he didn’t want to cut into the original wires for the FM interrupt. In both cases, the length of the cables/wires attached to the XM modules were plenty long enough.
If I remember correctly, my SO put together a small website with photos detailing how he did it: if you want, I can see if he still has it up and shoot you a link.
<< Knowledge is power. Power corrupts. Study hard, be evil. >>