I have an 03 Denali XL (Bose, factory non touchscreen nav, rear flip down DVd) and I would really like to ditch the non touch screen nav for a nicer pioneer or the like unit. My question is how hard is it to wire in everything to work with an aftermarket head unit? I know there are interfaces that allow the use of some of the factory options but I want to retain the use of all the factory options(including the rear DVD and steering wheel controls). What is my best options for doing this. Can teh factory nav antenna be used with an aftermarket unit?