I just successfully changed the water pump on my 190E 2.3, 1988. My pump was "growling" and it seemed to have bad bearings. Here is what I did. Take the fan off first. Then take the fan shroud and radiator off, noting which clips go where on the radiator. There are several hoses to remove, include trans cooler lines. Take off the fan pulley, and the fan clutch. Remove three bolts holding alternator support. Remove thermostat housing cover, thermostat, and lower thermostat housing. Remove water pump.
This was a good opportunity to clean out bugs and dirt from radiator, flush out coolant system, check thermostat (put it in boiling water to see if opens).
I did this with basic tools - 10mm, 12mm, 13mm sockets and wrenches. You'll need antifreez, perhaps some A/T fluid, o-ring for the thermostat housing, gasket for thermostat housing, gasket for water pump (gasket came with my pump)
Make a note of the order in which you removed the components so you repeat that order in reverse (this is where I went wrong!)
if you have any specific questions, send me an email.