Welcome, Janie, to the world of Thorns and Rohloffs.
I'll not re-cover the ground already mapped above, other than to say that changing a tube on my Raven-mit-Roholff is no problem.
One suggestion, which you may want to review with SJSC when you get your bikes: I've replaced my quick-release skewers with Halowheel "slow-release" skewers, both fore and aft. I found that my rear QR tended to loosen, although the front remained snug. The Halowheel fixed the problem at the rear. (The Halowheels use a 5mm hex key.)
Good luck, and enjoy,
Cheers, John