Some of the issue, like Samuel suggests, is about altitude. I know that I used to live in the Midwest, and when I went up my first big peak in Colorado, it kicked my butt big time. I'm not saything that you WILL have trouble with altitude, but I am saything that the adjustment to altitude is something that is unpredictable. Some people adjust rapidly, and it really doesn't bother them after the first day. Others adjust more slowly, and it takes them at least a couple of days just to feel normal at a normal pace. Then there is a small percentage of people who will not adjust well at all, probably less than 5%. But, if you have never been up high in the mountains at all, you won't know what you are walking into. It doesn't hurt to be in top shape, but that is no guarantee of altitude success. The good thing is that the north end isn't that high until you are about a half-day in. I think that Cathedral Pass is somewhere around 10,000'.