The key is going to be cardio, cardio, cardio..
Don't hike or jog with a pack, that is just stupid. and take it from me, you will create long term lower back issues with crushing disks..
I found that the more you run. (I mean getting to 5miles, and more) where you can run for about 30 minutes without getting tired. If you can run for 30 minutes, and feel like you can keep going, you are there.
Also, i would suggest that you start by also using stairs.. Stair climbers are great, and if you can get that thing going at 75% speed, and stay on it for an hour, there isn't a guide out there that will be mad at you for not doing your homework. I would also suggest that you work on wearing the boots and sock combos that you would use. Silk anlets socks under your normal socks will make the difference.
I don't go anywhere without Mole skin, and spray bandage. If you get a blister, dry it well, spray it, then put the mole skin on, and repeat at night so all night it bonds to your skin.
Good boots are the difference.
Once you get there, getting there a day early will also help, if you did your cardio homework, your first night will suck for sleeping, but after that you should be fine. Take Motrin, when you get there, and then take some in the am and PM before bed, starting this the day before leaving for there will help with soreness and the headache from the altitude. Drink water. lots.. if you are not watering the tree's once an hour your not drinking enough. I usually stop at dinner or you will be up all night going. But, as soon as i get up, back to drinking water, lots of it.
Best insurance you can get up there, is a life straw.. Those emergency small straws that you can drink right out of a creek.. they are like $20 and that and a lighter and whisle might be a life saver for you. Small and light.
Good luck, and good for you for taking the whole thing seriously. If your gonna spend the money, might as well make the most of it and not let your phsical condition limit your hunt.
Also practice shooting with high heart rate. (push-ups and then shoot kind of thing)