How to replace a 2001 Isuzu Trooper water pump and what tools I need?

This job requires the removal of the timing belt which is a good idea to replace while doing the job. Here is a guide for doing that (picture at bottom):

https://www.2carpros.com/diagrams/isuzu/trooper/2001

Then you can replace the water pump, here is a guide to show you what you are in for when doing the job:

https://www.2carpros.com/articles/water-pump-replacement

Start by draining the coolant and then you may need to jack the car up.

https://www.2carpros.com/articles/jack-up-and-lift-your-car-safely

Please let us know if you need anything else to get the problem fixed.