Garbage disposal stuck

[SLSL60]

I'm trying to remove an old disposal to replace it with a new one but it is stuck--can't turn it to remove it. So far tried leverage with a screwdriver, hitting that with a hammer, WD40, and right now I have some PB Blaster on it. Nothing has worked so far, so what else can I do? Someone suggested heating it with a hair dryer. What if I unscrewed the screws holding the assemble above it--would the whole thing drop down?

This is my first time doing this, so any suggestions would be helpful--I'm new at this stuff so I would require instructions!

Thanks~