That leak could be the speedometer cable or the bolts on tail piece. You might get lucky and be able to snug them up to get it to stop. Someone will chime in with the ft-lbs to torque them to. I just did mine good and snug.
That fill plug isn't as hard as it looks. You can get
this thing and it'll pump all the oil you need then you can use it on other stuff too. It won't work on gasoline though. Ask me how I know haha.