You are going to need some basic knowledge to replace a spoke, especially when it comes to drive side spokes and removing your cassette. I think on tour you could baby it with feel tension until you got to a shop.
Keeping some zip ties and having your wheel propped up while you true its about as simple as it gets, along with having the correct wrench.
I have gained a lot of knowledge in a lot of areas of bike maintenance. Outside of my normal job I work PT as a mech at my LBS. I did it for extra cash at first now I just do it for fun really. Most of my day is spent replacing tires, worn chains and every once in a while a overhaul. Bike maintenance is surprisingly easy if you just slow down and look at the problem and understand a high and low limit screw.
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rob E
There are people I have met in my time as a mechanic that just see a bike shop as a place that just does all bike things, it is not that they do not know how (this writer may not have known how), but they just would rather pay someone else to make it 100% right. In that same vein I am tired of hearing people say "knowing my luck I'd screw it up." You probably will screw it up, if you do not slow down and just look at a problem, its like any other problem thrown at you.
On the whole knowledge while touring. I think it would be a disservice to yourself to not at least own Park Tools Blue Book, we are given this book as mechanics and I still use it day to day, mainly for quick torque specs. If you go on tour with a tablet take a pdf of this book with you, there is so much information in there, we should all send Calvin Jones a Christmas card.