I have opposite problem/question. My house came with fireplace that has 8" tall hearth with slab on top which seems to be sandstone, and which now has a hole in it the size of a few quarters. I never liked the color anyway, and I would like to have granite instead. It seems the easiest least expensive make-over would be to just put a slab of granite on top of the sandstone (with mortar in between). Is this feasible, or is the sandstone too weak to support the granite?

I really like the simplicity of the room in its current state. You might want to look into installing a wall mural above the fireplace to dissuade you from hanging things above it or placing things on the ledge. It looks so nice clutter-free.

If you're going to continue to have the TV over it you need to take the surround to the ceiling. There are a million ways to style a fireplace. Since I can't see the rest of the room, what is your style? I think it would help you to look at photos on Houzz and create an Ideabook of fireplaces you like. Once you decide, a builder should be able to replicate what you're interested in. I assume it's gas? If so, you could change it to a linear fp if you don't like the traditional shape.

I wouldnt paint it. Its a very nice looking fireplace, and is already pretty neutral. Leave it for now, and live with it for a while. It can always be painted later, if you really dont like it.