Don, ask them to cap off the now-unused fresh water line, they can do that out of sight under the sink, I think. That way you won't have to mess around with winterizing that segment every fall.
Make sure to pre-purchase your consumables, and maybe some spares like an extra pee bottle and/or cap. Oliver doesn't give you any. http://store.natureshead.net
Make sure they use a large enough fuse, and have them label it! Since it will be a retrofit, they will probably use an inline one, and pick up power close by, maybe under the sink. Make sure it is readily accessible. The fan uses less than an amp running, but the fuse must be 2.5 to 5 amps as per Natures Head support.
Ask for a small led light so you can see if the fan is operating. It is audible if your tinnitus isn't too bad, but it is very quiet.
Get a 3 inch sewer to male garden hose adapter, so you can dump your gray water with a 3/4 inch hose. It's slow but very convenient if time is not a factor.
Post your thoughts here after having used it a while. I hope you like it. I am sure you will love being able to pass by dump stations and laugh at the lines. For off season and especially off-the-grid camping, it is a revelation.
John Davies
Spokane WA