Flooring Tile - Ceramic Tile in Fireplace Hearth

I have a fireplace that i dont use anymore, and the hearth is ceramic tile...I dont use the fireplace anymore but would like to change out the old ceramic with new prettier tile..The substrate is concrete as i discovered when one of the tiles popped up...The concrete is also cracked up the middle and the previous owner put the tile on top without repairing it so the substrate is not exactly even. My question(s) is....After i pull up the old tile (What is the best way to do this?) , what should I do to even the floor and fill the gap left by the cracking? I have never tackled this type of project before so your advice would be MUCH appreciated...
Thanks
Kathy

You can use a chisel and hammer to knock all the old tile & mortar loose. Wear safety glasses because chunks will be flying everywhere.

If the concrete is uneven you can use a grinder (like used for grinding steel) with a carbide grinding wheel to smooth it down. This will be very dusty and noisy and throw bits everywhere so wear earplugs, safety glasses and wear a good dust mask. Be warned that the dust will get everywhere. You will magically have dust everywhere in the house.

If the crack is small I would not bother filling it. If it is wide (maybe a 1/4" or more) there are patch compounds available or you can use a simple mortar or even some tile setting grout. This patch will add no strength so if the hearth is still moving the crack will reappear.