There are many alternatives for proper gasket material (if it is a simple joint) if you get stuck - but it's a nuisance if it doesn't work and you have to rebuild again.
Exhaust system gaskets need to be special, however.

Well, yes, those and head gaskets.

I used paint as a sump gasket.

We put just over 1 litre of oil in yesterday before it was up to the fill level. I will fiddle with the drainage bolt after Sunday !