http://youtube.com/watch?v=CxsTTU0zLdI
H7 - door panel removal for the w210 is quite basic and requires < 10 mins of
careful movement (so as not to blow the airbag if you have one). if you look
at the other links e.g door trim, they all seem to point to internally accessible
fasteners, though that is just my guess.
here are more videos, but again, they are for w210....
http://w210.pietrzyk.net/Default.htm