How to replace water pump

On a Yaris, the water pump isn't the worst job in the world, but you don't want to rush it. Drain the coolant first, get the belt and whatever's blocking access out of the way, then you can remove the pump bolts and swap it out.

Clean the mating surface really well before putting the new pump in. A lot of people chase leaks later because they leave old gasket material behind or don't seat the new gasket properly. Fill it back up with the right coolant, bleed the air out, and run it while watching for leaks and checking the temperature.

I'd take a few pictures as you go too. Doesn't sound like a big deal until you've got three brackets and a belt sitting on the floor and you're trying to remember where everything went. I've seen plenty of simple repairs turn into a headache because somebody skipped that step.