If you don't have a special bearing puller, then:
Kick out the old ones with proper diameter tool, use a nut or socket with the correct size diameter for example. You can damage the old bearing, you don't need it anymore, but please don't damage the bevel box'es housing surfaces.
Throw the new bearing's race into deep freeze and put the bevel box into warm place. With slight soft hammer help tap the new bearing race into paralever housing (kicking the whole bearing with hammer may damage the needles and the plastic support) and insert the rest of needles and bearing inside, same for both sides. Be sure you put the cone (race) in the correct side (see which way they're inside while removing the old ones).
