Check local code to see if you are allowed to have a propane furnace in a basement. Check to see if you are allowed to do work like this yourself. For sure, no matter where you live, a permit is a MUST.
Installing duct work is just one of those trades that looks like anyone can do it, but experience and training make a one day job out of what will take you several, and look like spaghetti.
First, you have the basement to work in, and floor registers or low wall registers are ideal for heat. But balancing the flow and air distribution are done by sizing the ducts, and sometimes with dampers. You could probably find on line resources to determine how many BTU are needed in each room, how many CFM that would need, and how to size the duct accordingly. But a contractor will have all that in his laptop.
Get a copy of the National Fuel Gas Code book. It is not expensive, and is available on google or a good technical bookstore. It will show you how to calculate gas pipe sizing, and how to make the flue. Both of these are critical construction details which can kill people or burn down the house, so be careful.