Depends on how important it is to you to have a working fp and whether you would be happy with gas logs. You can have a vintage mantel installed for a faux fp. Or get quotes for vented and vent-free gas logs and the associated vents/surrounds/mantels. If the chimney is still there, you could have a mason look at it and determine whether it is feasible to add a liner and reinstall a working fp. I personally like a real wood fire, and when house shopping I put a wood burning fp or wood stove near the top of my list of must-haves.

Wood burning fireplaces are ecologically a bad idea, and my eyes always burn when the neighbors, who are actually pretty far away, use theirs. A beautiful vintage mantel with gas logs might be a good way to go. Ours is a working fireplace that we never use because of the above consideration, but I found some pretty logs to put in the metal log holder, which look appropriate and much nicer than an empty fireplace. Obviously your own needs and wishes will dictate how you proceed.

I'd definitely add one. I'd do a vintage fireplace surround and a gas fireplace. That way you wouldn't have to rebuild the chimney.

However, I do have a 100 year old home with a wood burning fireplace and wouldn't trade it for the world! We use it all winter.