oil leak on craftsman model 917.378941?

If you can manage to get old seal off crankshaft it won't be bad but a lot of times you have to split the motor to knock the old seal out.
You will have to take off the blade and the hub it attaches to,use emery cloth on the crankshaft to clean any rust off(more for new seal so it doesn't get knicked)then try to pry old seal out without marring the engine housing.
You should put a film of oil on shaft before you put the new seal on.
You will also need something about the same size as the seal to tap the new one back in.

Bob
April 2012