Did that job last week-end along with the Water pump, belt tensioner, belt shock absorber and seal front engine cover.

The pulleys are attached by 3 X 13mm bolts. The easiest way is to loosen the bolts with the belt still in place.
Same for the power steering pulley.
Now, have fun with the bottom/rear water pump bolt.
It take small baby hands to get into that little crevasse to get access to this bolt.
Thys system is not the most brilliant system Mercedes has designed.