Well at least you got a good flush!
First I'll state that I do not have a 617, but a 616 I believe they are very simular, and by looking at pictures of parts on fastlane I believe I'm right on this in this area . . .
So it looks like you need to remove the fan, and the pully should come off with that . . . (I assume you know that) You then only need to pull the water pump (the bolts on mine do not go outside of the range of the waterpump pully) which looks like this:
You should not need to remove, and hopefully not replace ($$$$$$247.50) the water pump housing (Which is what I'm thinking you are trying to remove the bolts to) Looks like this:
The bypass hose I just replaced is a dealer item . . . cost me $13.20 + tax & shipping! I just bought one for mine!
Edit to add: Phil only stocks it like MB sells it . . . 1 meter legnth! $135 IIRC here is a DIY Link http://www.peachparts.com/shopforum/showthread.php?t=262523