There is very little squeeze room in the 190e 2.6, so, as suggested everything has to come out. If you have a digital camera, take images as you go so you don't get confused for what goes where when reassembling.
Your first water pump will probably take 8 hours - if not more. The second much less time.
Make sure you buy either a Graf, Lemforder, Behr or Laso pump. There are el cheapos out there on the market which are less than satisfactory in operation.
You will probably be better off also getting
New thermostat and gasket
New hoses
New tensioner,
New serpentine belt.

The job is stright forward and logical. The hardest part will be figuring how to get the fan clutch off. Search the threads here.
You will require the right tools.