2:35 p.m. on October 11, 2011 (EDT)
Karen,
you have plenty of places within a short distance of Lost Wages to try out your warmth/cold combinations. You are just a few hours drive from the Sierra and White Mountains (right on the NV/CA border). Reno and the Tahoe area are just up the road and already accumulating the winter snow. There is a Patagonia Outlet in Reno that has knowledgable sales people and really good prices on gear that is designed for exactly the conditions you are headed into. If you are a Sierra Club member, consider heading for Donner Pass and the Sierra Club's Clair Tappaan Lodge. Peter Lemkuhl, the manager, will be happy to go over layering and preparation for Himalayan trekking with you (tell him I sent you). Actually, you don't even have to be a SC member - all are welcome (members get a discount on the lodging and meals). And you could hike out to one of the 5 Sierra Club huts to spend a night in the back country. If you time it right, I might even be there to provide some mentoring.
Layering is actually very simple and common sense. There are basically 3 "layers" in the system -WWW (= Wicking, Warmth, Wind/Water). I use this in the backpacking and winter camping courses I teach.
The basic idea is pretty simple - the only complication is the plethora of possible choices. The simple combination is Wicking (1 pair of light, 1 pair of midweight longjohns); Warmth (1 pair microfiber pants, 1 DriClime shirt, 1 NanoPuff jacket, 1 softshell); Wind/Water (1 hardshell jacket, 1 hardshell pant/bib). Start the day's hike on the slightly cool side, and adjust the layers as the day goes on by adding or subtracting layers as needed to stay cooler or warmer and to get more/less ventilation/wind protection/water protection.
Now, the details (you can read this now or come back to it later) -
Fabrics - Your clothing should be wool or synthetic. Some people like silk for a very light skin layer. Avoid cotton. The reason is that cotton absorbs and holds moisture, plus the cotton fibers tend to collapse. The result is a lot of water that stays around and conducts heat rapidly away from your body. The good synthetics and merino wool wick the moisture away so it can evaporate and no longer conduct heat away from your body.
Wicking - the skin layer needs to wick the sweat and perspiration outward. This is where your long underwear goes. It can be either one of the modern synthetics or merino wool (merino is soft and does not itch, plus is somewhat wicking and tends to not build up a stink). The best of the modern synthetics is Patagonia's Capilene, though I also use Campmor's store brand. The longies come in 3 levels - light, midweight, and expedition. Separate top and bottoms are easier to adjust than a "union suit" or "Farmer John". You might find a light bottom with a midweight top is good for a particular day, for example. On treks, many people will take one light and one midweight set, starting with light, then going to midweight, then going to both if it gets really cold. You aren't going on the mountain, so the expedition-weight is not needed (unless you are really cold-blooded). You will want a "standard" underwear set of sports bra and "boy" panties (not strings, unless you don't mind the chafing). Ex Officio and a couple other companies make underwear that can be washed out daily and dry overnight that wicks well.
Warmth - This is your insulating layer. As with the longies, it is actually a combination of thinner layers. This allows better adjustment to the temperature than a single heavy layer. Microfiber works well for pants. (side note - get front-zip or full crotch-zip pants for both your warmth layer and wind/water layer; you will find it convenient as a woman on a trek to get one of the funnels so you don't have to completely bare yourself to answer the call of nature - practice at home first). You may also want a pair of fleece pants or one of the softshells, like Schoeler fabric. Patagonia, Marmot, Mountain Hardwear, Cloudveil, and other companies make pants and jackets from Schoeler and similar fabrics. Fleece jackets are good for the insulating layer on top. You might also consider filled jackets or vests, like Patagonia's NanoPuff and similar jackets that pack very small, yet provide a lot of warmth (and a wide comfort range). Marmot's DriClime is an interesting shirt/jacket concept that has a thin fleece with a windproof shell. On my last two expeditions (Antarctica and the Cordillera Blanca region of the Andes), my Warmth layer consisted of a DriClime shell, a NanoPuff jacket, a Marmot softshell, and when it got pretty cold, a Integral Designs Dolomiti hooded jacket). The pants were Patagonia's Alpine Guide pants for the Andes plus a pair of Feathered Friends down pants for Antarctica (you won't need anything that warm for your trek.
Wind/Water - this is your "weather-beater" layer. A Goretex or (my preference) eVent hardshell jacket is windproof plus waterproof, plus breathes reasonably well (eVent better than Goretex). I am afraid you will find that the PreCip jacket does not breathe well at all! Be sure your jacket has pitzips! When hiking in the rain (and on your trek, at the lower altitudes), you will really appreciate the ventilation of pitzips. Over the years, I have acquired several jackets from Marmot (best for me, especially the Alpinist 3 which is now worn out), Wild Things (order direct from their North Conway, NH shop - second only to the Marmot, and not by much), and Patagonia (haven't tried this out under real conditions yet, but looks like it will do well). Your soft shell jacket (and pants) are somewhat water repellent, but not really waterproof. So you do need a real waterproof layer. As for the pants, I prefer bibs, though a salopette-style is ok. Just be sure it has full side zips, both for ventilation and for the "dropseat" to answer the call of nature. Marmot has (had?) a full crotch zipper for some of their styles, which is pretty convenient for a quick #1 stop (if you have the funnel or in really cold conditions). A lot of people find, though, that hiking with Goretex or eVent pants in the rain can get overly warm. If your soft-shell pants dry quickly and/or are fairly water-resistant, you might be able to get along without a full waterproof/breathable pant. One thing a lot of trekkers do is just wear the wpb pant over the longjohns without another pant, plus use the velcro flap over the zipper to hold the sides of the legs slightly open for ventilation.
Oh, about the washing. You are in the outdoors. Everybody stinks after the first few days. You can wash the skin layers nightly and they will dry overnight, if you use the Ex Officio or similar underwear. After the first few days, no one will notice. If you get to a teahouse that has good shower facilities, take a long shower. Otherwise, don't worry.