W126 rear control arm replacement.
 

I'm up for a replacement of the D/S rear control arm on my 85' 380 SE. I found out the the car actually is slouching lower on the left side and the shock mount arear is actually starting to rust through.

What is the degree of difficulty in replacing this? This is my first Benz and have never worked on a RWD before. Someone please point me in the right direction before I start a fiasco.

Thanks,
Chris