Not really a big job. The water pump is located on the inside of the lower unit above the gearcase. Get a manual or hit the library. Another excellent source of info is the Search function on this Web site.
Ok, glad to see that it is a farely cheap part, and somewhat easy to do!! I did search the site, and seen that the main thing to worry about is lining the water tubes up correctly when you put it back together. Thanks!!