Apparently the altitude thing is having less atmosphere to protect us from radiation. It's not as glaring and hot as, say, Phoenix, AZ, it's somewhat more insidious. We don't get skin cancer as much, they don't get their thyroids and cataracts. My wife is an astronomer and her father was a pathologist, so she has a lot of medical knowledge.
I would recommend sunglasses, but that's a style choice. It's been 30+ years since I tried archery, though we have a range about 45 minutes away that I've been wanting to check out. I think progressives should allow you to shoot well with your bow, though you might want some range time before doing it in the field. I previously had no problem shooting pistols or rifles with iron sights when I wore progressives. For all my years in Arizona I never saw a snake outside of a zoo, and now that I'm in the mountains found out that snakes don't like snow, ticks don't survive up here either, we just have to remember to give our dog a tick treatment for extended travels.
Best of luck to you!