G'day Steve.It may be a bit hard with the motor & gearbox together but it is possible. I can't remember the seal size I used, 19mm id, 5mm thick, ?? od. With the g/box removed I ground off the rivets (clutch side) and carefully popped out the heads. New oil seal was a nice snug fit in the case hole then sandwiched between the two plates and riveted back together from the g/box side.Cheers