Here are some pictures from a 2000 Mercedes S430. 1st you need to remove the screw that is hidden behind the ABS sign and also the door latch area. Just use your fingers and pull up on the door panel from one of the edges but make sure you leave the trim on the door instead of on the panel.
(picture of right rear door)

Next you will need to use a hook tool to carefully pry/pull out the trim piece.
(picture of right front door)

(picture of left rear door)

When you have removed the trim piece, tape up the felt along all the sides to reduce contamination and you will have a very easy time with all Mercedes rollups.
(picture of left rear door)

When you put the trim back on, make sure you put some felt strips onto the trim pieces so it won't scratch the film and spray a little soap water onto the rubber strip so you can slide it back in easier. Hope this tips helps everyone out.
I will post pics of BMW door panels when I get a chance to take some shots.