I to wondered about that to on my 2006 f150 but I soon realized that on the bAck of the radio is the aux output you have to buy a 75 dollar adapter to go from the radio to a converter then to aux
I just removed my inlaw's 2008 gmc canyon factory stereo - no bose - but door chimes, and on-star - It has aux button.
I can tell you that I do not see an aux input in the back....I am guessing you mean a RCA female (ins) ...I only see the factory radio antenna in - Wire harness for main audio speakers - the one right by the it the smaller harness for the on-star I assume and that's about it.
Hope this helps.
By the time you get adapters to make your AUX play etc...I would just get an aftermarket double din.