from hiking to mountain climbing... how do you train?

Im in the northwest, so I have plenty of hills and mountains at my disposal. I usually do the local stuff, but I got a wild idea to go up south sisters in Bend, Oregon this summer. This is a huge leap from the normal hills I climb. I have all Summer to train and have started with go up the hills I usually do, twice. The past two weeks I have gone 10 times and takes me about two hours. My theory is, this is will help endurance. I use a heart rate monitor and average about 79% of my heart rate, it definitely peaks higher.

I have plenty of questions though.

If you use a HRM, what zone would you target for this training, do you try and control your heart rate or just push yourself?

Can you prepare yourself for the elevation factor?

What are the best foods for the energy needed. I plan to be at a calorie deficit for the most part of the summer but Im fully aware that I shouldn't starve myself on a mountain.

Any other suggestions or advice is greatly appreciated. The more information I have, the more prepared I will be and hopefully the less mistakes I make.

Thanks guys!