I have a 93 400SEL so I can't see mine being much different than yours. I just replaced mine last weekend.
You have one screw right next to the latch.
Two screws in the armrest cover look for the tabs on the inside of the armrest compartment that cover the screws.
One screw on the bottom of the door.
Then very carefully pull the panel away from the door. Don't try and completely remove it yet.
I took the ashtray out to help but you can do with out it.
From the side closer to the hinges you need to be able to place your hand in behind the panel and release the tap that holds the wood (aluminum) piece of the panel that looks oval and fall right next to the pull handle and above the armrest. That wood grain piece will pop out of the door. Then there are to bolts that hold the door’s handle to the door. Remove the bolts and pull the panel up to release from the door.
Be careful and look around before pulling on anything, don't use any force to take anything out and you will be just fine.
Let me now if you need pictures to describe this better, I just don't have them here.
1993 400SEL (W140) 281K
1999 S500 (W140) 163K (Sold)
2002 S500 (W220) 72K
1999 S500 (W140) 88K
You cannot simultaneously prevent and prepare for war.
Albert Einstein (1879 - 1955)