A builder in my area built 100 houses (including mine) with defective fireplaces. Basically there was no clearance between wood and the firebox and the johnney on the spot inspectors did not catch the problem in any of the houses until one caught fire. Oops.
So builder is fixing houses and I have 2 options. One is a repair of the framing which is complicated a bit by the fact that I have a finished basement (ceiling is liftout tile, at least). Basically they cut out joists underneath, add a steel frame and pan and pour in concrete from above then replace marble in front of fireplace. Sounds like a bitch to me but they have done it on about 70 houses though few have finished basments (most crawlspaces).
Second option is a gas fireplace insert. I have gas logs now and a glass door. Both will be removed and replaced with an insert that has a fan and also vents out (not a ventfree system).
Any suggestions on way to go? They prefer framing fix (slightly cheaper I've heard) and state it might be better for re-sale.