Bluebird 530A aerator gearbox oil question

Having a hard time finding a solid answer while searching the forums or web.

I have a bluebird 530A aerator, gearbox is leaking a little bit... I plan to split the gear case and re seal it. Does anyone know if parts will start falling out or is it pretty simplistic?

Last important part, what OIL does the gear box take? SAE30???

Thanks,
Justin