Hey there, thanks for the question.
How many miles on the engine?
does it seem to leak more after driving it and then parking it?
oil leaks can be tricky because the oil blows around while driving, but generally an oil leak that worsens when driving (noticed immeadiately after parking) and coming between the gearbox and the engine is a rear main leak. The seal is not expensive at only about $25, but the labo is high because the gearbox has to be removed in order to replace.
You probably want to start by cleaning the engine up real good and then watching for the leak early o when you first see signs of the oil to pinpoint it better and go from there.
I wanted to check back and see how you made out. If you need further assistance let me know please, if not just be sure to leave a kind rating so the site credits me for my time is all.
are you referring to the metal plate between the gearbox and the sump?
sounds like an inspection plate, would need a picture to be sure but if thats teh only place it's coming form then that gasket is likely the culprit.
If that's the case it probably just needs a new copper washer. If its a washer less magnet plug and not a drain plug then gasket sealer on the threads should fix it up.