it isn't hard, but it can be very messy and you can end up with a bunch of toxic old coolant spilled and/or stored in many containers in your driveway/garage. Except for my (now gone) old MR2, which had a complicated coolant flush/air bleed procedure that shops aren't familiar with, I have always chosen to pay a shop to change coolant in my cars because of the mess and the problem of disposing of a bunch of containers of old coolant. I would use a shop that works on a lot of Mercedes as they will be familiar with the bleed procedure and use the correct coolant.

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2005 Mercedes C230k sport sedan, 6 speed
1987 Porsche 924S - 968-engined track car