Yes it is that bearing #5. If your gaskets were leaking then you would find the oil dripping from the bottom of the transaxle casing, not the left side that you describe. The hydro fluid is finding its way into that left cavity and leaking from there. I suspect the bearing is the culprit, not the gasket.
When it happened to me ( I have a 1999 3205, almost same model as yours, with an aluminum transaxle casing ) I thought it was the gasket(s) as well. I replaced them and the leak came back. Finally my neighbor, who is a mechanic, helped me figure out the true cause and replaced the bearing. It wasn't something I could have done on my own. The bearing is not pressed in but, as I recall, some kind of silicone sealant is used to seat it. In order to get at the bearing, or replace the gaskets, you have to:
take off side panels
remove seat
remove all foot pedals
remove all hydro control handles
take off the fender/foot rest housing
remove gas tank
remove draw bar back plate
drain hydro fluid from bottom drain plug
of course the wheels should be off too
Then the back plate of the transaxle is exposed and you can remove the bolts and see what you have. You will have to replace both gaskets at this point anyhow. If you are reasonably competent mechanically, or are feeling brave, you can try it. You will at least become very familiar with your tractors innards. But before you do try it mow your lawn because you will need a few days ( I did ) to tackle this one. To tell you the truth I would recommend taking it to some dealer and let them do it.
Good luck and post your results when you are finished.
