I don't have the identical unit as yours because ours is an AquaHot 200. They should work pretty much the same though. I leave the electric burner on most of the time as that will provide you with sufficient hot water to wash dishes etc. Fire up the boiler if you're going to shower or use the furnace.
In answer to your question:
1. Turn on the boiler.
2. Set your thermostat to furnace.
3. Heat should be felt within a few minutes at most.
My system consists of several floor mounted registers that have their own fan system. It's very quiet and most times you won't even know it's on, you'll just feel the heat. It takes about 10 minutes to heat the coach depending on the outside temps of course. Between 10-20 degrees F outside, it'll take about 30 mins to bring the inside temps to about 70.
The unit should be checked once a year during your annual maintenance. There is a reservoir filled with fluid that needs to be checked periodically. Mine's in the propane compartment. It takes a special solution, NOT antifreeze. There is also a separate filter that should be changed annually. Mines in the same compartment. The filter also has a sight glass on it to drain any water so as not to contaminate the system. Usually the nozzle is replaced during the maintenance. Not a difficult job but access to the boiler can be difficult if you're a large person. I have mine serviced every two years unless there's a diesel smell or smoke from the exhaust when the boiler is fired...it's an excellent system and realtively worry free.....hope this helps....Dennis