Anyone want to jump in with advice? (fireplace / masonry)

The problem: the fireplace is made of grey brick, unattractive to begin with, badly stained by smoke before we bought the house. There is not a problem with the draw; the previous owner was apparently just a bonehead. We've used it without incident for 20 years, so I assume the smoke damage came from carelessness and not structural flaw.

I would like to cover the brick on the part of the fireplace that's visible from the living room - not the inside of it. I would like to use small river rocks, none larger than a golfball, and all of them somewhat flattened. Because the fireplace is large, I'd prefer to do that only on the part closest to the actual firehole, and cover the rest of the brick with beadboard.

Am I correct, first, that I need backerboard to cover the brick? What kind of mortar / concrete product would I use over that? Is this part of the project even feasible for someone whose experience is limited to carpentry / drywall household projects? How far from the firehole should I use non-combustible materials? (The fireplace is used only a few times a year, and the fires are never large - we do not rely on it to provide heat.) Should I work from the top down or the bottom up when setting the stones? Can I cover the whole thing with backerboard and install strips for the beadboard panels right over that? Will 3/8" backerboard support the weight of the stones? Can I add approximately 2" to the room-side of the fireplace without affecting the draw of the chimney? Are there other questions I should be asking but don't know enough to think about?

Any suggestions will be appreciated.

katie