My 2 cents worth - second everything everyone has said about Diamox. The advice we were given on my trip was to start taking it 1-2 days before your trip actaully starts at altitude - so start taking it when your train ride starts - I dont think you can OD on Diamox. The only person that bailed at our trip was the person that did not take Diamox.
The cold, dry air as well is a serious issue - take a scraf, bandena etc and keep it wrapped around your mouth to encourage moist warm air going down your throat. Up in those areas it's very dusty so minimise the dust your breath with the same set up. As others have said prepare for the worse and take a good cough medicine and good throat lollies. Suggest you also take some good heavy duty anti-biotics in your kit. You will have an amazing time and post some photos when you get back!