How do I remove my rear passenger door panel for my 1984 Mercedes 500SEL?

[84MB500SEL]

I think the window regulator in my rear passenger door is busted and I want to take off the door panel and look at it to see if I'm right, but I don't want to break the door panel. In my first attempt to get it off, it got stuck at the door opening handle cluster. Can someone give me the full instructions to do this correctly? Thanks.