My 89 525i is relatively easy. The only tricky part is getting the fan off. Make certain you have the gasket with the pump. Most people recommend that you remove the radiator (which isn't difficult) but generally you can get by with it in place. Replace the water pump hose at the same time. If you have a timing belt, replace that as well since you have already incurred most of the labor. By a water pump off the internet (Zygmunt). The Laso pumps I think are the best. You may want to get a book for assistance, Chilton or Bentley.
I need a new water pump. I am thinking of doing the service myself. Does anyone recommend this for a weekend warrior? What are the specific steps?