Is it possible to SAFELY put a vent free firebox into a wall and put an antique mantle around it?

I'm wanting to put a fireplace in my living room and someone offered to give me the gas log fire box. I can cut a hole in my sheetrock wall and it will go into an unused kitchen cabinet in the room on the other side of wall. Would it be safe to slide the logs and firebox into the wall? What precautions need to be taken or should I not try it at all - dangerous?