plumber torch & heat it slowly, or wrap some sorta heat blanket around it (you'll want to concentrate the heat on the bearing itself), which should allow the bearing to expand, making it easier for removal. now to get one on, you can use a heat plate & let it heat up for 20 min or so, & it should slip right on.....just remember it will be very hot!
there is also a retaining ring on top of the bearing, you have to bend down the tabs with a flat head screw driver, then the bearing will come out