I have done several extended expeditions, up to three months, over hundreds of miles, with heavy weight, to altitudes over 23,500ft in Nepal and Tibet. There is no substitute for experience when you are going to be away from civilization for extended periods. In that region of the world that starts when you leave the airplane.
If you are going to be out there for a month you will go crazy in a bivy. I am also not a fan of sharing a tent with others. Snoring, flatulance, and leaving to pee will get on your nerves and test friendships for no reason. I carry a The North Face VE25 ($425.00). At 9lbs this is my one weight concession. It is a three person 4 season dome which will stand when others fail and is nearly water proof. Bibler probably makes the best tent but they are hard to find and more expensive. If you have a month of gear you need a big tent. The weight is not that much greater for the comfort it provides. The next most important item is you sleeping bag. Marmot makes the best by far. Stick to down as they weigh less,pack smaller and last longer. A Marmot Col bag which will go to -20 ($600). I have used this bag to -40. Do not wear a bunch of clothes in the bag, this will reduce your warmth. Stick to a thin set of long underwear, I prefer Mountain Hardwear ($45 per set). Thermarest sleeping pad ($55). With all of this weight you will need a good pack. The BEST and IMOH only option for 80lbs and up is McHale
http://members.aa.net/~dmchale/. This you will not find in any store except his in Seatle, WA. He does however take phone orders and requires your measurements for custom fit ($600). This is an internal frame pack. Externals are a thing of the past especially if you are going off trail. They are less stable and get snagged on trees an brush. Make no mistake you will not be under 80lbs probably closer to 100. His packs also break down to ruk sac size for daily use after you establish a camp. Throw in antibiotics, a sewing kit for flesh, water purifier (PUR Scout $80), stove (MSR XGKII $80), 5 fuel bottles ($20ea), two pair polar fleece ($120 for top and bottom), good stiff boots to carry the weight ($300) be sure you break them in extensively, a multi tool ($40), Waterproof (Gortex) top and bottom Marmot is best ($600), flashlight (try to get LED the batteries will last longer $30), Cookware(save weight with titanium $90 with fork and spoon), the list goes on but those are the majors. Food is also a concern. Better of with dehydrated prepared foods you just add water to. They are about $4.50 per meal (actually supposed to be a two person meal but I eat a lot). You will not want to go through a lot of effort when exhausted. I have these in quantity if you need them. They are also light weight. Best is Mountain House for taste and price. Everything else is available at you local outfitter (buy now winter gear is reduced) or at
www.rei.com.
Bottom line: You will spend $4000 to be prepared for winter. This is not a negotiable sum unless your life is.
I am not trying to discourage you. Self reliance is a great accomplishment. I can't understand this country where most freak out when the electricity blinks. The sense of satisfaction at the end of your trip will be second to none. Be prepared though. You do not get a second chance at survival. If you prepare well you will come away with the attitude, 'what was the big deal' as I do. If you don't, well.....