I've got a force 10 diesel heater on my 29' sloop. I installed it myself, so i should be able to answer most, if not all, of your questions.
> How is the best way to plumb it?
I have mine plumbed using the same 1/4" marine rubber fuel hose that feeds my engine, but i do not feed the heater from the same tank .. i have another 40lt tank specifically for the heater. I don't use a pump of any kind - i prefer a gravity feed. This does mean that on extreme heels i can lose the heat, and sometimes air gets in the lines and i have to either prime the syphon (mmm tasty) or bleed the air through the filter or by blowing through the hose to force air into the tank. This last step also creates a little bit of pressure in the system.
So, i don't have any hose clamps on the heaters fittings, so i can pull them off and check if the fuel is flowing, and take steps if it isn't.
> What is the best fuel to use?
We run our engine on 100% bio-diesel. For the heater, in the dead of winter we like to mix a little petroleum diesel as it burns hotter and doesn't coagulate. I have never tried kerosene, but i suspect it would be easier to light, if anything
> When lighting; how do you prime it by burning alcohol?
You pour about 1oz of something flammable (Alcohol or camp fuel work well, gasoline will do in a pinch) down there. Never (well, use caution) do this when the unit is hot, as it will explode a bit and scare the hell out of you, if not injure and maim. Do not pour from the bottle, but rather a small container you keep specifically for this purpose. When you're poured, wipe the container with a tissue or some tp. You're going to light this tissue and quickly toss it inside.
Let it burn for 10 minutes until things are nice and hot, then turn the fuel on about 1/3 of full until the flame goes very yellow. Once it's all yellow and still burning, you're good to go. Crank it up and enjoy.
Be careful not to flood the thing with liquid fuel .. you want to be burning the vapours only. It's also important to keep the little hole in the center clear of soot and debris.
> How hot does the exhaust get?
Hot as hell, especially if there's a decent blow out. I've seen a full 1.5 ft of the exhaust glowing red. That said, the deck vent stays cool enough to touch most of the time. I've noticed that the deck area around the chimney has begun to delaminate a little, and i suspect it's due to the heat.
If you've got any more questions, i've gotten to know this little unit quite well over this last winter.