Hello, and thank you for chosoing Just Answer!
Which engine is in your Trailblazer?
4.2, 5.3, or 6.0?
Yeah, I seen it...Sorry about that.
There is a bug in the system that doesn't show us the optional information, when we first look at the question. Then when we post needing the information it's there...VERY frustrating, for experts. Hopefully not as bad for you, though.
Anyways, HERE are the instructions you asked for about the water pump on your 4.2 engine.
The job calls for 3.1 hours of labor, so take your time....and PLEASE don't get frustrated at it..it will go.
If you need anything else, just let me know!