A few months ago, due to an accident, the fixture itself broke completely. As in, the socket that the light bulb goes in smashed and broke off.
I want to replace the light fixture entirely and have bought a new one. However, the screws holding the old one up are so old and rusted that they're entirely rounded off. There's no way for my screwdriver to grip it, so I'm not sure how I can remove it.
I considered just prying the thing out of the ceiling and drilling new holes right beside the old ones, but my porch is very old and I'd be afraid of damaging it.
What can I do?