So once you are done you don't have to leave the SD card in correct? It's just used to program the radio and then you are done with it. The Nav that is installed is it Google Navigation, WAZE, OnStar or anything like that? Can you tell where they are getting their maps and directions from? I am think about doing this potentially as I use NAV alot and thought it was installed too - not having to hookup or have your phone all the time will help and be more clean.