might consider making your own gasket
It's easy. Just get a standard office folder, cut out the basic shape and put it on the surface. Then take a light hammer and tap around the edges. You now have a gasket. Apply a little glue and bolt together.As far as oil, it's not a high RPM machine so I would just make a guess from the thinkness of the oil as to what grade (30, 40, 80 or 90 weight) it is and replace with a standard automotive oil.