My experience is that just visiting the country for a couple of months will give you a new perspective on life in general.
Though i did a light 10 day residential meditation course in Tibetan Buddhism upp in Mclead Ganj i really feel that it was the trip as a whole that made the big difference for me. I didnt do any volunteer work or such but the dignity and humanity of the Indian people in spite of poverty really made an inpact on me.
Long train rides without a seat reservation is really a humbling experience, having nothing to relly on other than the kindness of other people in order to be able to sit down or if you're lucky, even sleep.
It made me reflect on how I chose to live my life and what I can do for others.