While you are at it plan on checking/replacing the belt tensioner too. I recently replaced my water pump (1986 300E) and found my original belt tensioner was shot. Additionally replace the hoses, thermostat, belt and use the correct antifreeze. It took me 8 hours to perform all the work but I work slow and methodically with some of the time spent cleaning while I had access. I removed the radiator and fan just make things easier but many feel it is unnecessary. The most challenging step for me was removing the bolts on the water pump, not that they are tough to access but they were incredibly tight.

Do a search in this forum and you will find a wealth of information regarding water pump replacement. The information I found was all I needed and I never had to reference the manual.