Need plaster demo tip
You can use a sawzall reciprocating saw to score around the edge if you think it's necessary. Don't plunge too deep, you'll want to beware of wiring and such...you shouldn't hit anything, but just hold the saw at such an angle that the blade BARELY gets through the plaster.
It is a messy job to demo plaster. Make sure you wear a good mask. It is also a good idea to create a dust barrier between your kitchen and any adjoining rooms. Use palstic sheeting to do this. Tape it to the cailing and walls or around doorways to seal it off the beat you can. If you need access to the room where you have plastic, hang the plastic so there are flaps that overlap sp you can get through, but when they are at rest they seal pretty well. Good luck...I don't envy you.