I went to a Nepal and didn't get anything worse than a stomach ache, so i wouldn't worry. The only things i would recommend (once you're there):
Drink Bottled water only, check the seal. Wipe the top of glass bottles before you drink from them. Don't have ice cubes, they're always made from tap water. Only eat hot or frozen food, nothing from markets etc without cooking. Be wary of people who offer to carry your bags at the airport, & animals/pets. If one person orders food for all in a restaurant it'll come on one plate(!). Finally, collect as many business cards for your hotel / favourite restaurants / shopping districts as you can, because the taxi driver won't know where it is.