ok I am going to send you some instructions shortly straight out of a GM repair manual , must warn you though this is not typically a DIY project. But if you think you are up for it I will be more than happy to help
Water Pump Replacement Removal Procedure
Inspection and Repair Procedure
also to do this repair you have to remove the balancer here are the removal instruction and specail tool required
The balancer is a slip fit and should slide off.
During removal if the balancer could be turned side to side the pin is worn.
anything else I can do to help you ?