Just changed one of these myself, I heated the case in the oven (make sure the case is nicely degreased and the missus is out first) at about 150-160 c for half an hour and the bearing just dropped out, should make it easier to press the other seals out as well.When installing heat the case again and put the bearing in the freezer for a bit before assembly.

Remember when removing the impeller from the shaft that it has a l/h thread and you will need a holder to hold the gear.