Has anybody change out one of these?
Where did you get the part?

Wow, I'm the only 1 with a bad one of these.
In any case, got one from Autohause for $206 shipped.

Dealer wants $275 plus tax-$60 (core) and $16 for the coolant, which is not bad (the coolant that is). I am a little wary of places that charge for cores, that only means they sell rebuilt and not new.

Sometimes I'm amazed also at the lack of replies to questions.
Regardless, I did mine which I'm assuming is little bit different from a six. If your water pump is anything like mine (ML55) then take your time and make a diagram where all the bolts go since they're not all the size size or length.
Other than that it's fairly straight forward, just take your time and remember to use either the Mercedes coolant or the correct replacement. Don't cheap out with crappy coolant!
By the way, you may want to also think about changing your pulley and tensioner at this time also.

Thanks

There are several writeups on this Aux Pump repair on other Mercedes Forums. Repair for just a few dollars and alternate parts which are the same from other auto manufacturers that cost around 20% of the Mercedes part coat.
Mike