Will I get home sick? Nepal for 4 weeks? Voluntary work?

Me and 2 of my friends are wanting to go to Nepal next year through an agency called project abroad or something! One of my friends wants to do medicine for 4 weeks, one wants to do teaching for 4 weeks and i cant decide between teaching and phisiotherapy? It would be for 4 weeks next July just the 3 of us! I will be 17 then and so will one of my friends, the other will be 16! My two freinds are defo going but i cant make up my mind and they need to know asap! The longest ive been away from my parents is 5 days, i dont know if id miss them too much! Im also a very fussy eater and a vegetarian! I spent SOO much money on clothes and going out at the weekend! I dont know if i could give it all up! it will cost just under �2000 i have �1000. I know im being selfish because i want to buy clothes but i also realise its a great oppertunity and would be a great thing to do and ive always wanted to do it but i dont know if im too young? Should i take the oppertuity? Will I not get home sick?