Yes, all the screws need to come off to get the cover off.
I posted a very detail description of removing the blower motor, including a step-by-step instruction for removing the wiper arm assembly. I did it once, and detailed every step as I was doing it.
I had a click click in the blower motor, and thought the motor was going out, but in my case, it was debris that got in there and was rubbing against the blower fan blades.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".