Looking at pics only of the X4/10 fuse block does not appear difficult to remove and replace. You have a couple of wires that attach and that would be the first approach. I would detach wires, but protect with tape or rubber plugs to cover the leads, especially the big red lead as that comes from the battery and it will be hot with spark. After that it looks like a couple of nuts and it is off.
Why are you swapping out the X4? Alternator issue? Just curious...

deucer

 

The alternator is not charging the battery and the x4/10 150 amp fuse has blown.

 

Well reason enough. Not hard, you can do it. Just cover the leads then reverse installation.

 

I think that my first action would be to disconnect the battery ground cable...

 

Why not disconnect the battery completely and be safe?

This post from the W215 forum stickys might help. Fusing of W215 & W220 is similar.

http://www.benzworld.org/forums/w215-cl-class/1625470-w215-hidden-fuses-revealed.html