Headache can be nothing more than lack of water in your system. Staying hydrated at high altitude is of serious importance. The amount of fluids lost is huge. Take a purifing filter with you so you can refill your bottle from small creeks up high. Saved my butt sheep hunting at 13,000'.
BOOK YOU WANT A BOOK!
"Elk of North America Ecology and Management" You can get it at Amazon.com.
There is a gentleman that lurks here, AKA Elknut, go to his website. If you really want to learn you have a lot of work a head of you.
First trip out here shoot the first Legal elk you get a shot at even if it is a cow. Remember you are dealing with a point restriction in that area and 55 is the same. Keep asking question and I will keep answering.
Gselkhunter