In order to replace the bearings, they need to be pressed on/off. If you don’t have a press, you’ll need to take them to a shop to be pressed.
Alternatively, if you’re considering upgrading the shafts to 4140 or similar, the new shafts often come with the bearings already pressed on. Though you probably won’t need 4140 shafts unless you drive with a lead foot off road or run 35s.