Easiest way to tap into aux?

Hi All,
I just read the Chris Dragon Rip Your Dash Apart guide - yikes!
i'm adding xm radio (an external unit) so i'd like to tap it into the back of the cigarette lighter (i'll buy a kit for that) and i'd like to run wires behind the vent - i see i need to take the panels around the steering wheel off - i can live with that.
is there an easy way to tap into the aux wires? i was originally going to run a 1/8 wire from the receiver along the carpeting to my center console - then i realized that was silly - i'd instead prefer to rip (or buy?) a wired 1/8 jack, and run the wiring to the back of the radio and tap in - i did see a post with pin locations, but not with wires - i'd really appreciate an idiot's guide of what the wiring on the 1/8 jack represents, and where/what colors to tap into. also, a method to get back there without removing the radio, if possible, would be great as well!
thanks so much!

 

can any kind soul offer help or advise? Thanks!