The hardest part might be separating the motor from the impeller. If that goes well, the rest is a piece of cake. The first time I pulled my impeller I had to take the thing to a motor shop where they used an acetylene torch to heat it up and pull it (I was working on a different problem than you). The second time I did it, but it took a fair amount of pounding with a brass punch to do it. Impellers don't lend themselves to just using a normal puller to remove.