you have a sheep tag? unlimited unit?
I'd say cardio cardio cardio, but what I need and what you need may be 2 different things.
p90x, heard good things, heard yea it works if you can do it/keep up, but good luck at that! I'm sure you could if you can push yourself.
and what do you mean elevation changes hurting your body? altitude sickness? coming from low altitude? eat your fruits/veges at altitude! no booze/caffeine. plenty of water, relax recover, day 1 I wouldn't plan on running up and down mountains, or at all unless you have to! slow and steady wins the race.