Adding engine heating to diesel heater

[osprey877]

I currently have a hydonic diesel heater that uses either shore power or a diesel burner. It provides both domestic hot water and cabin heat by means of small radiators and fans. I would like to add the option of using the engine heating so that when I run the engine I also heat my domestic hot water. From what I have been able to glean from the internet, the best way of doing this is to plumb in a separate heat exchanger into the cold water supply to the water tank (this is the way a Hurricaine Combi unit is plumbed into the engine coolant system, according to their online installation manual. It says don't mix the engine coolant with the hydronic heating coolant). Assuming this is correct, I have a few questions:
1. Is the new heat exchanger plumbed in series, or in parallel with the existing engine coolant loop?
2. If in series, do I need to worry about the ability of my engine water pump to handle the extra load?
3. So long as I keep the new plumbing below the level of the engine expansion tank, do I not need to worry about air locks in the system?
4. How do I get the water in the hot water tank to cycle through the heat exchanger in order to heat up the tank? Or do I put it on the hot side of the tank and just have "instant hot water" as opposed to a tankful of hot water?

Thanks for the help.