I assume since you are a resident of WA, you are going to have a guide on this up coming Dall sheep hunt. Actually, your outfitter should provide you with a list of things that you will need on your hunt. You mention that weight will be an issue. You are correct in this assumption, not only in regard to what you will have to hump around, but you are also limited to a certain weight when flying. Therefore, only take necessities.
As far as optics are concerned you really only need to take a good pair of binoculars ie. 10X50's. Your guide should have a good spotting scope so the both of you can critique the ram once spotted. Most of the actual spotting is done with your binoculars first. There is usually plenty of time in most instances after the ram is spotted to set-up the spotting scope for a detailed look.
Make sure you don't skimp on quality on any of your gear, you will regret it with every agonizing step. Take a good, well broken-in pair of mountain boots ie. Lowa , Meindl or something comparable. Also good quality hunting/hiking socks are a must ie. Wigwam ingenius or Bridgedale ascent or like quality. And while on the subject of feet, take a good look at your feet before you go on your hunt. Make sure to cut your toe nails and address any potential problems such as in-grown nails or corns, before you leave home. As far as clothing is concerned, take no cotton garments. Go with good synthetics. Polartec makes some excellent undergarments, as well as pullovers and jackets for layering. These are light weight, breathable, packable and quick drying. Outer garments need to have the same characteristics. I carried one pair of pants, they were a pair of Mammut Champ pants. The top I wore for the most part was a Polartec pullover. I however, like the looks of the Sitka hunting clothes, I might have to look at these closer in the future. Light weight, packable rain gear is also a must. I used Cabela's Dry-Plus Spectrum ultra parka and pants. One other item I carried was a pair of light weight hip boots called Sourdough Slippers. These are made by Neos, I purchased them from Barney's Sport Chalet in Anchorage, AK. They are great if you have to make many stream crossings each day. You will find a lot of quality gear for mountain hunting at Barney's. You will most likely have to supply your own sleeping bag and pad. Here you also want to go with a good synthetic because it will dry faster than down if it gets wet. I used a bag that had Du Pont Quallofill with a Thermarest prolite 4 pad. Both would compress into easy to carry stuff sacks. To carry all of your gear you need a good backpack either internal frame or external. Which ever you decide to go with make sure it fits you properly. Take time to go over your pack thoroughly and adjust it for your body. Your hips should bear most of the load not your shoulders. It's a good idea to use your pack in your conditioning program. Load your pack and take it for a walk, here you can determine any problems. When I was preparing for my sheep hunt I would load any where from 50-100 lbs (most of the time 75-80 including my rifle) and go on a 5-8 mi trek.
Another important item is a good First-Aid kit. You should also have some moleskin and spyroflex blister dressing for any blisters you might get. This kit is also a handy place to keep toothbrush, toothpaste and deodorant.
Bug/Mosquitoe spray, don't forget.
On the issue of food, on a backpack hunt it's usually something like this:
Breakfast-instant oatmeal (easy to pack, easy to prepare, and good energy source) plus a protein bar.
Lunch-will consist of something like Mountain House or like meals. Here you just add hot water and about 5 min. later you have a very tasty meal.
Diner-will again most likely be Mountain House or something similar. Here you need to get ample protein to help your muscles recover. So I would also have maybe 2 protein bars.
When you talk with your outfitter ask him about the food. He will most likely have ample amounts and good quality food for you and your guide. I bet if you discuss this with him, he would be willing to supply certain items, that you like. The only food items that I brought with me were chewy granola bars (in between meal snack) and protein bars. However, my outfitter had supplied us with a variety of such items.
I would recommend that when you talk with an outfitter you discuss in detail any and every concern you have with him, for what these hunts cost he should be more than willing to answer all of your questions.
Hope this helps some. There is actually a great article on the Home page by Michael Eichele titled Gear for Dall Sheep Backpack Hunting. As an AK resident he gets to go more often than most of us in the lower 48 can dream about.
Check it out well written and full of good advice.