You should have a winterizing bypass with your water pump configuration, as set up at the factory; I'm not sure why Sean is using a manual pump. It isn't hard to stick the plastic tube in a jug of pink, shut off the line coming from the water tank, and turn on a hot water tap til pink comes out. If you don't know where your water pump and valves are, it's probably behind a carpeted removable panel like ours is, in the wall below the cable TV and a couple 120v outlets in the passenger side storage bay. The casing for all this extrudes into the adjoining tank bay, where it can benefit from the heating unit there.
That at least covers your rear regarding the spendy AquaHot. But as long as I was at it, I'd likely do the whole job, get several gallons and pump through all the other plumbing fixtures, including any icemaker. A cup of pink in the drum and cycled once will do a washer/dryer unit. I usually blow out the system first, including cycling the icemaker even though it has heat tape protection. But if you are confident in your building's temperature maintenance (it wouldn't fail in a power outage, say), at least doing the AquaHot would offer fail-safe peace of mind re. super-expensive repairs.
The links mentioned by others should help with details.
Joel