nav radio
i too want to do this, but i want to convert the non bose to bose wiring and cant get any help anywhere on this. ive pretty much given up. anyways, in my extensive internet search, i found that what you want to do is possible. you can get a none bose stock OEM nav radio to install in your truck. ebay has them and they are GM OEM. you may need an interface unit to keep bluetooth, onstar and the like compatible with your radio, i believe its called a PAC interface
(the PAC is followed by different numbers and letters indicating its particular use and compatability) try this website for more info
http://www.pac-audio.com/productDetails.aspx?ProductId=384
i hope this helps you in your endeavor, but all ive seen indicates that your project is pretty easy to do.