Removing a spring tensioned lip seal requires time, patience and tools.
If you have a COMER gearbox you may need a seal spanner wrench
to unscrew the seal retainer from the front of the gear box and a very
big heavy vise to hold it.
You will be better off removing the gearbox and taking it to an ALLIED implement
Dealer or a competent farm machinery repair shop and let them do it for you as
you will want to have both seals replaced as a matter of good practice as the
bearings should be looked at as well as a blown seal is an early indicator of
roller bearing failure.