It is good to be able to do wheel maintenance oneself, but the world won't come crashing down if you cannot. I have been riding bicycles for almost 45 years, and I have never had a broken spoke. I don't even carry spare spokes when I tour.
The most likely thing to go wrong on a tour is a flat. The ability to patch a puncture (or replace the inner tube) is the most important skill to have. (I usually get one flat per 7 - 20 day trip; one of my touring friends has a mountain bike, and he goes years between flats.)
I take-in the slack on cables as I tour, and make similar minor adjustments. Other than that, when something goes wrong, I start hunting around for a bike shop!