Oh man! I'm so envious of you! I'm another one who has dreamed of doing something like that for years. DH and I talk about it when we retire and get the kids through college (7 more years!!!).

I have done a lot of hiking at higher altitudes and it is interesting until you get settled. I'm sure you know this, but pay attention to your heart rate, not your breathing as you'll be huffing and puffing no matter what you do. It's a little alarming at first, but you'll get used to it. If you start to feel panicky and have trouble breathing, stop. Stand still for a moment and do whatever you do to relax yourself. It's a very typical response, actually. Know that just because you have issues breathing at say 13,000 feet, it doesn't mean you will at 14,000 feet. Weird, I know, but I always know when I'm at 12,500 feet on a hike - I get whiney, miserable and lose all motivation. If if push past that, I'm fine. But, do thoroughly know the signs of altitude sickness. It can come on fast and without warning. We climbed Mt. Whitney, and knew we had to "rabbit down" when our friend, a very intelligent computer scientist, could not figure out how to tie his shoes.

Sorry, I tend to ramble. Just have fun!!!