Question on transmission fluid leak
 

We recently purchased a 2002 Mini with 103k miles on it. Base model with 5spd. After bringing the car home we noticed it was leaking transmission fluid pretty bad. From what I can tell the leak is coming from where the trans and engine mate together so I would guess a input shaft seal leak? We also noticed a little slipping while driving so we believe the clutch has gotten oil on it as well. Has anybody else had a leak like this and where was it coming from? If it is the input shaft seal, is it replaceable? We plan on doing the work ourselves especially after seeing the great write up on the clutch replacement here on the pelicanparts webpage. Thank you for any help or advice.