Ok, first and formost, i am not really talking about chaning a tire. I have done that many times on the road, and at home. So I am over thinking this to a degree I am sure.
In my "kit" i carry 1-3 tubes, patch kit, little mini multi tool, some ziptyes, patch kit, tire iron's. I like the suggestion of carrying directions on the derailleur, since i did that with my first flat, which is a nice way of being prepared.

So for the chain, I just need a link, and tool. I'll start reading about the wheel, but that is not going to be easy

I think most of it is just having the confidence to ride in a strange area, in the dark, for 200k. I find this to be a little daunting. My biggest concern is time, and therefore getting stuck in the night somewhere. On a century the best i have finished is eight and half hours. My longest ride at 118miles was closer to 12 hours. My computer tells me I do around 13.7 mph over long rides. So I feel a little thinking is in order on the next go around. Well i can keep talking, or I can go ride my bike.

cya