That engine has a design problem where the #6 cylinder drops a valve causing severe engine damage. This is a well known problem for the 650 HP ISX. The cure is a redesigned cylinder head to prevent. If I had to guess, this would be the cause for the rebuild.
Ouch!!!! I wish they had better/more pictures...so hard to tell how the coach was set up.
A previous ad for that coach (#1401) indicated that it swallowed a valve at about 78,000 miles. It has a fairly standard front entry layout other than the couch is on the curb side with the desk and most of the kitchen on street side. The bed is on the street side with a shallow cabinet on the curb side containing a TV on a lift. Rear bath with center half bath based on an extremely poor quality floor plan I have. Looks like the 1/2 bath is next to the refrigerator with a ariston stacked washer/dryer across from it. Sub Zero refrigerator/freezer. Fisher & Paykel DishDrawer.
For what it's worth, the non-Newell images in that ad are from it was for sale in PA, last year. I was in the coach at that time, and it was very regularly maintained at Newell by the prior owner and stored indoors. The Newell image is also from sometime the past, as well, but it is representative of what the coach looked like. It had carpeting in the salon. I recall that a number of the windows were replaced due to failed seals, I think. I tossed my notes from it, so I'm sorry that I don't have more for you.