Some advice on what to bring and what not to bring on a 120 mile trip.
 

Long trip for me, but most of you would probably consider it short: 120+ miles/ 3-5 days. I'm going to have to pack light, because I'm taking a train to Colorado, carrying the bike (which will be partially disassembled) to a bed and breakfast near the train station, putting it together, getting on and riding for 60 miles, staying a few days (riding 5-10 miles every day), turning back around, riding back to the B&B, staying overnight and repacking the bike, and getting on the train the next day, heading back home.

By the way, the B&B has generously allowed me to keep the box in which I'm taking the bike at their place for a few days until I come back, so I won't have to carry that on the road.

So, the question is: what do I take? What is the bare minimum for such a trip? I'll have a backpack, but I don't know how I should outfit the bike for storage. I guess that's part of my question, too.

I can't say I'd pack any differently than I would for a short ride. Tube, patch kit, co2 inflater with 2-3 cylinders, and multi tool. I assume you can figure out your clothes and toothbrush and stuff, I'm not your mother. With a place to stay and food available, modest ride distances, I don't see this as needing anything out of the ordinary. If you were say primitive camping with a tent and cooking all your own meals with a camp stove, then there might be more gear and prep involved.

Spare tire, a few extra tubes, pump.