1997 E320 Water Pum Repair - Cost

We have a 97 E320, 85,000 miles, Automatic. We have a 2-3 tablesppon daily leak. Our neighbor figured it out, coolant. The repair shop couldnt figure it out until we told them and now they tell us we need a new water pump and it will cost 750.00. Is this reasonable? ALso do we have a timing belt and should that be changed also?

THanks