I have a 2009 CLS350 Grand Edition that came with an after market android head unit' I purchased a second hand original unit which works fine. I wanted to update the sat nav but it turns out that the part number of the unit I bought should not have sat nav! Someone said it must be a "mix & match" of a couple of units due to issues with the CD loader in early versions. Does anyone know how I can find out which DVD I need to update it, the unit has a 6 CD changer and plays DVD's?