Wall Mount Gas Heater Hookup

I just purchased a 30,000 BTU wall mount gas furnace and will be mounting it in my dining room and connecting it to my two 100lb LP tanks located on the opposite wall (outside) about 25 feet away. The tanks currently supply a gas range and there is a Tee with shutoff valve jn the basement ceiling directly below. Question is, can I snake a flexible gas line across the basement ceiling and up to the dining room to the heater or do I need to use rigid pipe? I'm not a plumber, but I know how to plumb more or less. Is this a project I can safely tackle myself or is it best to contract it out to a professional? I'm pretty confident I can do it myself but have never installed a gas appliance before.