Struggling with the same issue....even my wife's new Traverse doesn't have NAV....I've got an excellent A/V guy here in St. Louis....JML Audio.....he'll figure out a way for me to get it integrated, make it look factory, and still continue utilizing all of the factory capabilities.
When I sat in NUMBER3's 1LT a couple days ago, this was one of the things I was thinking about and GM did NOT make this dash aftermarket "friendly" as all of the controls and faceplate are one integrated unit.
Good luck! Suction cup on the dash is the best I can offer you right now...
2SS/RS, VR, Blk hockeys, Blk leather, MN6, sunroof, GFX
Delivered: 29 June 09 !!!
'57 BelAir 2Dr Post
'07 Avalanche LTZ (daily driver)
'10 Traverse (wife's demo)
'99 Harley FLHTC