I have one of these cars (the Oldsmobile version of it).
Changing the serpentine belt is a pain, the first time you have to do it. I do hate removing that motor mount. Don't even try to use a wrench on the serpentine belt tensioner. I use a ratcheting serpentine belt tool. Specifically the Lisle 59000, and I love it. It's made in USA, and you really do want a ratcheting serpentine belt tool. I have used it many times as a close quarters long arm ratchet, and it's worth having just for that. I bought it to use when I replaced the LIM gasket on this car.
In so far as replacing the water pump, it does look easy on this car. If they had the 4 cylinder version you don't want to know how hard that would be to change out!!!