Replace lower mirror plastic part.

Part 7 in the attached diagram.
I have a few questions on replacement. I understand how to take off the top glossy part. But can the lower outer part be replaced without having to take the entire mirror off? How is this replaced?
Secondly, our model has the puddle lights but i'm confused when looking at parts.
My options are:
w/o memory and w/o logo
w/o memory & w logo
w memory
I would assume i need the w/o memory & w logo? I'm not sure what the memory part is??
Finally, whats the best pricing parts website to buy OEM MB stuff?
Thanks!
https://mercedespartscenter.com/part...=Mercedes-Benz
http://www.benzpartsdirect.com/


