318 P218G Oil leak at front crankshaft?

Hi all,

A few weeks ago I noticed a small oil spot under the front of my 318. As it had been cold I did not investigate until now. It looks like the leak is coming from the front of the engine where the crank shaft exits the block under the PTO clutch. Is there a seal there or is it just a main bearing? Also is this something that can be repaired with the engine in the tractor? I have browsed through both the tech manual for the tractor[TM1590] and the engine manual[CTM2] and did not find what I was looking for.

Thanks for any advise,
Mike