Ben, this is a good DIY job. I would suggest flushing (a degreaser first, then citric acid) as long as your working on it, and new coolant, if the current coolant is more than two years old.
Also, you may not have to remove the fan/clutch. Some MBs have a fan shroud that can be taken off without having to take the fan off.
MBenz, maybe I misunderstood you, but did you say you have 375,000 km on the same coolant? The normal MB recommended change interval is 3 years, I believe. Even if it still looks clear and clean, I'm not sure it would still have the proper anticorrosion properties.