Earthlark, I have that Nashbar Essential Tool Kit, and I think it's a good place to start, especially if all you have in terms of bike-specific stuff is a portable multitool. IME, the pedal wrench is cheap and soft, I guess use it as long as you can, plan on getting a better one once the jaws are mashed up. Also, the tire levers, although impressively large, are not very strong, and may break if working with extra tight tires. Turn to Pedro's levers here, they're the best. Other than that, I think it's a very useful kit for the occasional hobbyist bike maintainer. In particular, the allen wrench set with the ball-ends has become my
#1 go-to.
I suppose I may as well lace a new rim for the experience. I've trued my wheels a couple times, so I suppose this is the next step.
Well be careful there, I thought the same and just tried to completely loosen (not even undo and relace) all the spokes on a cheap wheel I obtained specifically for practice, and when I was going through tightening everything back up, I didn't pay nearly close enough attention and before you know it, I've tightened that sucker into like a 2" taco! I loosened everything again as quick as I could, and it seems the rim relaxed mostly... Obviously I don't have any answers for you, other than go slow! which is what all experienced wheelbuilders tell newbs all the time anyways.