I have a gas fireplace in my natural gas heated home and am wanting to convert the fireplace to a wood burning insert. One because I enjoy wood burning fireplaces more and two as an emergency backup heat source (our power went out for a couple of days last month). The firebox is fairly large (24x30x30), but I have no preconceived notions that I can shove a wood burning insert in, run a liner up the chimney and start burning wood. In this situation, is it general practice to rebuild the entire firebox and chimney. Before I go talk to a professional, I'd like to know what all I'm getting into here. Thanks for any input!