Welcome to the mad house! We specialize in crazy here. Although we might give the "you're crazy" look, usually there'll be encouragement to go for it anyway, too.
As for finding a bus, you might recall the Utah legislature passed a measure in their last session allocating money to help school districts replace the older buses in their fleets. This could mean there'll be an increase in used buses coming available, but there's a catch: the old units are supposed to be moved out of state or destroyed. You might be able to find a way of moving one out of state temporarily, at least on paper... just sayin'... The first step would be to learn from the transportation departments whether they'll be disposing anything that's interesting to you. Many of us weren't so lucky to find something near and traveled hundreds to even a thousand miles to bring "the right one" home, and it could be that way for you too.
There's a "public service announcement: don't buy a CAT engine" thread here, and it's only partly tongue in cheek.. I don't have any personal experience with CAT though.
I've been so mired in "little stuff" getting around to my roof raise that it's becoming difficult to isolate how much work is related to the raise specifically. The level of work involved in a roof raise depends on several things, including: how do you want to fill in the newly created void on the sides, vs how you'd do it if you were to just remove windows (or even not at all); how do you want to adapt the raised roof line to the front and rear end caps. I guess there's a spectrum of easy but patchwork to difficult but polished appearance.