Agck! Don't count on getting film there and don't even dream about having any local place process it. But yes, a stash of your favorite ohh-so-soft toilet paper would be a good idea.
Himalayans? You HAVE to bring the big camera. There will be so much there to inspire you, you'll kick yourself silly if you don't have it with you.
I am so envious of you. Our trip to India was truely a life changing experience for us. When my kids are older we are going back, no question about it.