RE: Altitude sickness
I just got back from North Western CO. I had a great time!! I life in New York at about 300 ft. above sea level. We flew to Denver and backpacked to 10,000ft. all in the same day. There were four of us and none of us had bad altitude sickness. One of the guys had headaches for the first few days.
I think the best thing that you can do is get in great shape! All four of us on this trip had been running or biking everyday for months. This was my fourth trip and the first two I was not in great shape and experienced headaches.