I don't know how your newer door panels come off, but most of these that I've worked on are held on by small snaps that clip into the back of the panel and then pop into the body of the door.

To get the panel off take out all the external screws that you can see. Some, like the two that hold the door closure strap, are hidden behind behind little flaps at each end of the strap. The actual door opening handle on my car has a black plastic cover that is inside the recess behind the handle. This cover pops out and reveals a large screw. On the rear edge of the door is a chrome surround at the door lock. There are two screws there. There may also be a large screw that holds the arm rest on the door. Look under the rest.

To remove the actual panel I use a flat pry bar like a 'Wunderbar'. Start at a bottom corner and push the bar in until you feel it stop. Twist the bar. This should pop the clip out of the door. Slide the bar along the bottom popping out each clip. There is probably about 5 or 6 clips. Work you way up the front and back sides. At the window my panel just slips under a cover and is not held in by screws.

In my experience, esp. with older cars, there is always a few of these clips that come out of the door panel and stay in the door. Door panels on old cars were made out of a type of Masonite which weakens with age. This is why you need to be careful to get the 'V' notch in the pry bar on either side of the clip like you were going to pry out a nail.

Panels on newer MBs are made of fiberglass and do not split as easily, but, the clips still come off the panels. The clip assembly can easily be glued back on.

Hope this helps.