What condition is the plaster in over the gunite?

Is it 'hollow' sounding when you tap it with a hammer? Any plaster flaking off?

Resurfacing will probably require you to take off some if not all of the old plaster.
They probably should have acid washed the plaster before they painted...or better yet never painted in the first place.

Sorry for the bad news, but doing it right is going to be a lot of hard work.