It should not be that hard of a job. However, I don't know if you work on cars and what your criteria for a bad job would be.
Without seeing your car, I am going to guess that it would be helpful to jack up the car and remove the wheel from the water pump side so you can do some or most of the work through the wheel well.
Break loose the bolts from the water pump pulley first, then take a ratchet or breaker bar and overcome the idler pulley to slip the fan belt off. Yank the pulley, take the pump bolts out (paying attention to the position and the length of the bolts in case they are not all the same.)
(I am assuming it was a given to drain the radiator first and into a clean bucket if you wanted to re-use it).
Before we go any farther, what is your car's problem? It may NOT be the water pump and this is a pain to do for nothing. I have NEVER seen a water pump go bad that did not leak around the water pump, so if you have a bad head gasket blowing exhaust pressure into the water jacket and causing coolant to not circulate and to overheat the engine, it may not be the water pump at all.
If you could give descriptive symptoms, I could be of better help.
Anyway, to continue, after the pump is out, scrape and clean surfaces with a razor blade and spray cleaner and rags.
When installing a new water pump, I put motor oil on all the bolts for the next poor soul 150, 00 miles down the road. Also for me if I have to pull it off tomorrow.
Put a bead of high temp red or orange RTV silicone on both sides of the gasket. After you tighten the bolts, you can wipe off the "squease out" silicone or just leave it there to dry.
Good Luck! Without a description of you symptoms, I cannot tell you that the water pump is the real problem.
When someone asks, "How do you do this?", I start with "Why do you need to do this?".
Just trying to help,
Saturday, April 5th, 2008 AT 11:22 PM