When l purchased the truck, it had the 2004.1 Nav DVD, so l switched my 2007.1 Nav DVD with it....Now the Nav screen is blank, and it indicated that it is updating my position, how long will this take..........As well, when l follow the instuctions for installing all 6 CD's in the changer, it won't allow me to install them..l hold the 3rd button for 2 seconds, it lights up, then the 1st light indicates, that it is ready, but the slot won't open......l'm assuming with the changer thier, that l have a CD changer, am l doing something wrong.....One last one...l have the seat memory option, but l can't put the driver's headrest all the way down...Am l missing something ???????Thanks for patience...Wonderful Vehicle...........

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2006 ML350