What ever happen to just removing the deck, raising front end for access (placed on jack stands for safety), sliding underneath the mower, dropping the crank pulley/ PTO clutch, and then remove and replace the seal. I usually have both the jack stands and the jack in place, just added measure of safety.
But of course I not afraid of getting down on the ground level either. It is also a good time to check the undercarriage and deck for problems. A good clean paved or concrete floor helps so can use a creeper.