Hello I will help you with your question,
The cost to have your belt replaced is $75 for the belt and 5 hours labor so at a shop rate of $85 per hour the cost is about $500 but the water pump should be replaced at the same time as the pump is driven by the belt and if it fails the result will be the same as if the belt broke on its own..
The pump will add 2 hours to the cost and the part is $175 so another $345
Let me know if you have further questions about this
Glad to help and thank you for using JA!!