Well, here's a rear door panel DIY, the front works similarly except you will have the challenge of having to remove the seat adjustment switches without trashing them. Can't give good advice for this other than take it very slowly and pry gently...
http://www.peachparts.com/shopforum/tech-help/205929-lets-pull-rear-door-panel-w124.html
I think there are also some front panel DIY's in the Wiki.
Rgds,
Chris W.
'95 E300D, 380K