Typically, a sheep is a large white aiming point. If you think you need more than 4x for any range at which you should be shooting, then you'd be wrong. Google up the subtension of a 4x duplex leupold reticle and get back to me.
On the other hand, using the fat part of the duplex for range estimation can be worthwhile as well. IIRC, the 6x leupolds subtend 9" at 100 yards, and your sheep/muley chest is ~18" deep. Good enough to firm up a 300-yard range estimate when your RF gets dropped or is otherwise TU. If I can't fit half a sheep chest between the fat points on the vertical hair (~400 yards), then I know I need to get closer. I've not used a LRF on a mountain hunt, though I have one. If I do ever go LRF, I'll put turrets on a 4x leupold to mess with heads...
You need three layers of pants: medium weight thermal underwear, some sort of DWR treated quick-dry 4-way stretch walking pant, and lightweight rain gear. I use merino wool, then either REI mistral or some sort of mountain hardwear earth-tone walking pant, and patagonia rainshadown rain pants. Some see fit to spend huge $$ on various pricy gucci camo mountain hunting pants that typically have too-few and too-bulky belt loops, which are well suited to bunching up and giving you a nice heat rash under your heavy pack's waistbelt on a long hot packout.
On top, I take a lightweight thermal t-shirt, a heavyweight thermal top, a puffy insulating layer, and lightweight rain gear (Mountain Hardwear Cohesion jacket).
Gaiters - save half the weight over crocs and get OR verglas instead. Don't leave home without them.
Hiking poles: If you find yourself on something really steep and slippery, you'll regret not having something to arrest with. I take a 100cm ice axe from SMC in Ferndale, WA and use it as a cane on the flats and an arresting tool on the slick steeps. for the other hand I take a Black Diamond boundary 2-section ski pole for a walking stick.
You'd better inquire as to what kind of spotter your guide has, and react accordingly...A pentax 65mm angled with an XW-10 or XW-14 eyepiece will give as good a view as about anything, for not too much $$. You won't be able to use much more than the 39x given by the XW-10 eyepiece when the mirages start.
Take a pair of UL running shoes from vibram or new balance or whomever, and do your stream crossings with those. They weigh nothing - about the same as crocs, and are WAY more useful around camp and such. Or, for small shin or knee-high streams, tighten up those gaiters, tie a string *tight* around your ankle and top of calf to seal things off, and give 'er hell.
For training, if you've trained to the point that you can spend most of a day hiking on steep terrain without blistering feet or hurting yourself, then your cardio will have taken care of itself.
Crampons: stubai aluminum 10-point strapons are the standard.
