There is no way to replace the water pump on this engine without removing and replacing the timing belt on the process. He is wrong about the "tune-up" etc. If the water pump leaked onto the belt it's now likely to fail and was probably due for replacement anyway by the time the water pump wore out. I would not recommend, based on what you have said, to allow this guy to work on your car at all if he didn't get the timing right and didn't try to get you to buy the complete service which would have included a new timing belt, tensioner and camshaft and crankshaft seals. Any less than the complete job is a risk to you and any mechanic who is liable for damages due to his neglegent work.