The water pump isn't nessicary but most people don't change the coolant unless they change the water pump too. The water pumps do go bad, that is not abnormal. And when you replace them you lose most of your coolant. It's not something I would do until you need to, and that goes with the coolant too. I would wait on the coolant until the pump fails. I made that mistake and had to buy the coolant twice.