That leak could also be coming from the transmission. Easy way to determine the source: Drain the belly pump (remove the pipe plug at the bottom) and remove the belly pump drive coupling. Then run the tractor around for a few minutes and see whether you still get oil dripping from the area.
If you do find it's the tranny leaking, either the countershaft or mainshaft seals (or more likely both...) need replacing. You'll still have to drop the belly pump to get at the tranny seals, but it's a straightforward and inexpensive repair, and you won't need to split the tractor.
