I use the wrench method, a thin breaker bar can also be used, tight fit but I have one I got from GM good wrench that works, barely, I would imagine it could be imposible with the motor or sheet metal slightly shifted either direction.
Warranty time is 1.5 hours.
I don't know enough about the quality of different aftermarket brands to say if AZ has a good one or not, they all change vendors and re-builders so fast it is hard to say what you will get. I would just get the cheapest NEW pump I could find unless the price differance was HUGE then I would get a lifetime reman
Chilton and haynes both suck!