New 06' Executive Owners... Ride Home

I agree that AGM's are really a great option if you need new batteries. However, it sounds from your description of your house batteries that the previous owner may have installed a battery watering manifold system like Pro Fill or Qwik Fill. They are great systems and make it very easy to top off wet cell batteries. Most have a squeeze bulb that you attach, drop the end in a jug of distilled water, and pump the bulb until it gets firm. If you have that type of system and the batteries are otherwise in good shape, I would keep them until you need to replace.

I agree with getting advice from various sources but it sounds like with your current family obligations and the nature of your questions that your best bet would be to take the coach to one of the stellar shops in the Junction City/Eugene, OR area and let someone get it up to snuff in terms of service items. Premier in JC, Oregon Motor Coach in Eugene are highly recommended. The Aqua Hot is a great gizmo but it is a complicated beast. You can certainly do the basic service yourself (change burner nozzle, clean combustion chamber, replace fuel filter) but folks with the proper test equipment and certified to service Aqua Hot/Hydro Hot units would be my choice for a good service and checkup. There is also a Cummins Shop in Coburg, OR that gets good reviews.