How to change a pto oil seal on a 18.5 hp briggs & stratton

Hi,
Faced with this problem, I would dismount the engine from the frame and invert it(turn it upside-down) and take a screwdriver to pry out the old seal. Putting the new one in is a bit more challenging since you you must make sure the youdo not cut the lips on the keyway. It is supposed to be installed slightly below flush, but flush will do.
Peace,
Clarke