What would cause oil leaking from around the shaft under the motor?

Hi Holly, It sounds like your bottom seal on the engine is gone. This is a common thing because there is a lot of tension on the drive pulley attached to it when the deck is engaged. To replace it, the pulley has to be removed and the engine removed. It is quite a big job. I would suggest you get some one with some experience to do it.
GOOD LUCK

JOHN @ RONA
September 2005