Help with Retiling Fireplace

A friend of mine asked me to post this. Thanking you in advance for any advice you can offer. I'll pass it along.
"You are good at these. I need to see if I can stir up some direction and wonder if you could plug this into an appropriate forum to see if you can get some feedback. I am retiling my fireplace. In doing so, I've had to strip off a layer of granite tile and ceramic tile. I have it down to the brick except on top of the hearth where it appears they built the hearth up about 2 inches using a cement. Getting the tile off the top of the hearth has been a real chore I presume because it wasn't set right on top of brick but a much more porous surface. Do I chip it all out? Should I regrout it? How do I repair the edges which are real rough - I presume I have to get those back to 90 degrees again. How do I prepare that surface so that I can put wonderboard down and then retile?"
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