Ceiling box? What kind of wiring is it? standard romex style bundles? Chances are the lazy electrician never hooked up the ground and just left it dangling. If this is older construction then getting a ground there will be, um, harder.

You can do a little better with an oscillating multi tool. You'll still have a lot of cleanup and repair after the tile is down.

“[...] tools don't get socially interesting until they get technologically boring.” ― Clay Shirky, Here Comes Everybody: The Power of Organizing Without Organizations

Chances are the tiles are fixed to the floor with mastic. Carefully pry them loose with a putty knife and wonder bar. then store them away somewhere safe for when you want to re-use them. Fill any significant voids with plywood or floor leveling filler before you cover with the flooring.