Kent,
We have the same coach. The Hydro Hot is the same thing as an Aqua Hot. Vehicle Systems, the manufacturer, changed the name a few years back to sound fancier. Other than that, and the size of the tank, they are the same components, and system.
If you are not familiar with how it operates, there are some good pictures with flow charts on the website,
www.aquahot.com. We have had our Monterey for 8 years, and it has been the single steepest learning curve, among many.
Even if you don't use it like a full timer, it should be serviced once a year by yourself when you become an expert, or a certified aqua hot tech. Especially, change the nozzle, change the diesel fuel filter, and clean the combustion chamber.
To access the inside of the metal box (it has a double hinged lid) get on your hands and knees and look under the bay door. You should see two black rubber plugs. Pry them off, and use a long phillips screw driver to un-screw the screws holding the lid down. Over time, when its time to put them back on, you will learn to use a magnetized screw driver to hold the screws in place while you stick the screw driver back through the holes under the bay door.
Bill Sprague is absolutely right. You must winterize if you are going to store the coach in cold weather. Temporarily in cold weather is okay if the ambient temps rise above freezing during the day. Your coach has a thermostat that will provide heat to your water bay, and the aqua hot components when the temperature gets below a pre-set threshold, usually around 43 degrees F. For it to kick on, the diesel burn switch under the kitchen counter must be on.
Good luck. Its an awesome system once you learn it relatively well.