If you run a wood stove boiling water directly, the steam will be at 100C. If you run a coil through a fire, the steam might get hotter than that. FYI.
I think the cheapest way would be to just put together a couple of steel drums, the bottom one to contain the fire, the top for the water, and regular pipe up to the still boiler, then a copper coil through it, led downwards, and then led through a worm or a truck radiator, to a holding tank that had a level siphon or float valve with your boiler. You could even design the whole thing to nest inside each other, to save transport space. If you wanted to be real efficient, you'd make a real rocket stove as the bottom chamber:http://photos1.blogger.com/hello/175/78 ... 0stove.jpg
These are nice, since you get the wood to burn twice.. once as gas, once as charcoal.
Just some thoughts
I'm sure some grandpappy has done all of this before..