I just read a very detailed description of taking off the armrest on this site the other day. Search and you'll find it.
I remember reading the post briefly, and recalled that the screws for the armrest are underneath the seat back. So naturally, you have to take off the seat back first.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".