I recently inherited a 2000 GMC Jiimmy that has alot of juicy options. 1 that I am curious about is the Aux input. It has a Bose HU and an Aux button so I assume there is an input somewhere. How do you use the AUX input? Does it need a special wiring harness added or is there a plug on the back of the HU? Any info/help would truly be appreciated.