First off, many thanks for your service to our country!
I was Peace Corps Cameroon in 1988/1989 in Cameroon, West Africa. Seems like yesterday, hard to believe it's been over 20 years. We trained in The Republic of the Congo (Zaiire) and also in Cameroon before posting, for me that was in a tiny village that had not had foreigners since the French pulled out....
Water will be your biggest issue, but Peace Corps has pulled their heads out of their butts since the 1960's and realized that quality water filters are an intelligent investment, or at least they were on that track when I was in service. We used a ceramic gravity filter that handled about 2 gallons at a time. So I would inquire of your handlers, but not really worry too much about water. However, keep in mind it is up to you to be ON TOP OF YOUR WATER. I was sick a fair amount of my two years from waterborne stuff simply because on occasion I would forget to bring my own filtered water and in the tropical heat, there was no way to spend a day in the villages without water... presto you have some new bug. You have to be dilligent ALL THE TIME. Thats as simple as just making sure you have a full water bottle in your pack ALWAYS. Not usually, but ALWAYS.
As mentioned already, music is a nice touch stone to home when away from home. Bring your iPod and a small decent speaker system. Batteries are available even in the most remote of Timbuktu villages, I would not worry about that. I brought a solar charger and sold it pretty quick because it simply could not provide enough power to run my player and external speakers... but my motorcycle battery did just fine!!!
Other than that, everything you are going to bring will wear out before you leave so don't worry about it. Clothes will all be available there too. I brought a small photo album of my family and friends and carried it with me whenever I went to do my Aquaculture visits in the villages.... it was by far the single most important thing I packed. Family translates across all languages!!
Again, thank you for your service. PM me if you have other questions.
PS. What program are you going to be in? Your chosen program will dictate, to a large degree, the size of the city/village you will be posted to and therefore the conditions you will live in (running water, electricity, paved roads, etc). Ditch all your existing notions of what you are getting into and open yourself to the experience. Enjoy!!!