Couple things that I have always looked at planning one of these to Colorado.
Bear identification:
http://fwp.mt.gov/education/hunter/bearID/Montana actually requires this for your black bear license. Not a bad idea for elk/deer hunting either as any shot is nothing but a dinner bell for a bear.
Train as you'll work. Put together a pack and go walking with it. For the army, every quarter we'd do a 12-15 mile road march my last unit. Once a year, we'd do 20 miles. Monthly it was a 5 mile. With rifle, field gear AND a 40lb rucksack. Even at 220 lbs, I could do this task. But it's definitely a lot easier at 190 or less. When I suggest a pack, I am only thinking a day pack here what you might need. Ask your guide what is normal there.
There will be no substitute for altitude. Don't know when the last time was you were in the mountains, but I notice it every time I go out west and do manual labor. It takes a couple days to adjust to it. May want to plan accordingly.
Couple weeks back, I had the good fortune to ride a horse for about 2 hours. Not a trail animal either. Equestrian stuff for the SCA. Working a line of poles and knocking heads off of those poles with a wood sword. My hips hurt for 2 days afterwards. You'll definitely want to work with a local stable to get used to riding. May want to even consider riding and then walking for a couple hours a time with a pack on. If you can think you'll do it in the hunt, try to do it here too. Especially carrying a rifle AND a pack. The strain it puts on your shoulders and arms is entirely different.
Consider getting and practicing with shooting sticks. They are nice once you figure them out. For shooting sticks, consider getting a couple of ski poles for walking with for balance. It will help in the inclines. just something my cousin has suggested to me and he lives in Boise ID area and hunts elk every year. They work good doing double duty.
As to mounting from the left....
http://www.lemen.com/qa176.htmlhttp://cha-ahse.org/store/pages/151/WHY ... FT%3F.htmlSafety.....
But I don't think you'll be carrying a sword with you. But tradition has been from the left because that is normally the side a right handed person has his sword carried on.