Being a 30 yr diy'er with the past three working on MB's I would say go for it. Take your time and plan on tearing into alot of the front of that engine. You want to consider what all parts you want to change while you are in there. Cooling fan clutch - I would figure that it is getting about time to change it at 130k - stuff like that.
Not sure about the newer ones but you get an opportunity to see the real engineering in MB's in the W123/126's.