Firebox lining and other basic questions

I have an old house (1939) that has a fireplace and chimney. The chimney has been capped. The sides and ceiling of the firebox appear to be sheetrocked, the base is lined with ceramic tile matching the hearth. There is a gas pipe line that is also capped running into the firebox. There is a large mantle made of wood around the firebox. I am trying to determine what needs to be done to make this a working fire place. My initial thoughts are to line the firebox and perhaps tile it with soapstone or satillo tile and install a ventless unit. I want to see if this is a viable solution. I also want to get an idea of what material should be used for lining etc. Any information would be great.