ORIGINAL: timcat26
I've had a similar situation and I wound up dremmeling and drilling the screw heads out. After that, soak it in sone Nitro fuel, maybe overnight, and begin trying to work it loose. If this doesn't work then I would go to heating it to try and work it out.
Would it not be more sensible to try the heating first. The heat will not damage anything but the dremmeling sure will.