I've seen homeowners that can't screw in a light bulb (or are afraid to), and others that do major remodels; hard to characterize an average homeowner. If you have reasonable mechanical aptitude, it is not that hard. If the flange is in bad shape, then it becomes a much bigger pain, something to consider if it is the only toilet in the house.
The Totos that use the unifit adapter will work on a 14" rough-in. It comes with the 12" version, but the 14" can be purchased for it.
My unprofessional opinion.