Well Mike, --TIP : "after removing the upper radiator shroud", removing the belt is the easiest step! Suggest having this done by a mechanic or get help from a car savvy buddy whom is handy with a wrench! REAL HANDY! IF you must try this, search youtube, watch video, then you decide!!
Ps: ALL ENGINES/SAME PROCEDURE. So 'which ever' one you have it will be about the same! 4.3L - 5.0L - 5.7L. Gas - but the 6.5L Diesel is different! So just enter "change water pump on a Chevy" on youtube search. Same video for the GMC. Just more video available for Chevy. Watching it being done is much better than reading it being done!