I bought a used Mercedes. It's supposed to have navigation. Well it does, but it does not have the navigation DVD. So I have to buy the DVD, but that's where my knowledge about it ends. On ebay I saw that there are DVDs for given model/year and year of maps. For example, DVD for 2006 E-class with 2008 maps on it. So if I buy a DVD for 2008 E-class but I have 2006 E-class, then it won't work? And do they make DVDs with maps from 2010 or 2009 for models from year 2006?

If I buy a DVD with maps from year 2006, could I just download an upgrade to a 2010 map (or do I need 2010 DVD nav?)

And does the DVD has to be at all time in the DVD drive, or do I copy it to a car's memory, if it has one.