Well, to be able to work on it the easiest, remove the entire pan bottom then you can work on a bench without laying under the bike.
You could also drill them out with left handed drill bits/extractors, but yes you will need some new ones.
A good local hardware store may have some without them having to come from BMW.
M6x20mm is the screw size for the filter cover, the pan mounting screws are M6x25mm if you want to take one of them to the local store for sizing....