I generally prefer to hike in long sleeves and long pants in Glacier. It keeps down the amount of sunscreen that I have to worry about. I have a long sleeve wicking shirt that has vent panels on the back and zips up the arm, under the armpit and down my torso. So when it is warmer, I can open those up and ventilate. Same goes with the long pants and a zip down the side of each leg. When you are in camp, you can zip them up and keep warmer.
I agree that down is the way to go. It will give you the most bang for the buck. I carry a down vest with elastic waist and arm bands to keep my torso heat contained. A light pair of gloves or cloth mittens help as well (in fact, your extra pair of socks can be worn as gloves). But probably the biggest help would be a wool or similar cap. It is lightweight and helps minimize a big source of heat loss. A lightweight waterproof jacket will also help since it creates a vapor barrier that helps maintain heat and humidity.
Some lightweighters would say don't carry anything else. When it gets cold, retreat to your sleeping bag. I personally don't fall into that camp.
Now to many this may seem heresy, but there is a lot of hype around Gore Tex. There are many fabrics that work much better in pushing water vapor out. Gore Tex is overwhelmed too easily when you are hiking in the rain; you get soaked in your own perspiration. Look at this PDF to give you some ideas about different fabrics.
http://www.verber.com/mark/outdoors/gea ... bility.pdf For true Gore Tex, You would be lucky to find anything under a pound and many weigh close to two pounds.
If you want something that is waterproof, but breathable, look to eVent. If you want water resistant, but breathable and lighter look to Epic for example. I even like some soft-shells for their breathability and ability to ward off light rain, but many would disagree. If you are staying on-trail in Glacier, for rain gear I generally use a sil-nylon poncho with thumb loops and snaps. Good ventilation, lightweight and it covers not just you but all of your backpack. And for those toilets that do not have a roof, a poncho works better than a jacket.