I don't think I saw an answer to your shorts question--yes, you will definitely want more than 1 pair. I'd say 2-3, to be safe. You definitely don't want to wear them twice without washing--I've seen a few tales of woe from gals who have done this. Also, they are meant to be worn sans-underwear. Most of us really find it more comfortable to use chamois butter of some sort, as well. My favorite is an all-natural product called "That Butt Stuff." I tried it because the name made me laugh, but it's really a great product. I will also use Brave Soldier Friction zone for my longest rides on any trouble spots or spots I suspect could become trouble spots.

Good luck! What a cool adventure!