The truth is, weight does make a difference, but how much that matters to you is a personal decision. When you're pedaling for eight hours a day, those extra pounds start to grind you down a bit. If you intend to tour for more than a week or two, I would suggest that you pare down your weight as much as possible, and I would use panniers front and back on the 520 (a bike which I happen to like quite a bit), rather than a trailer. Definitely leave the repair stand at home. You will be amazed at how helpful people will be if you run into trouble with your bike on the road. As for the MREs, they weigh about a pound and a half each, so I wouldn't plan on packing more than a couple of them.

Good luck.