interested in oncology?

I believe that i have found my calling. i am wanting to do oncology but pediatric oncology more... if pediatric oncology i cannot get a job i will perfectly satisfied with oncology. it seems ever sense my grandmother (whom i loved so much) passed from cancer all through her body i have been wanting to do this but been hiding it cause i am such an emotional person and noone thinks that i can do this but i know i can! can someone please tell me what i should do? i am in the prenursing program and will transfer to a 4 year university very soon. i am wondering where can i work? i know i want to work at a hospital for at least a year to gain experience. but where else could i work? what else should i do to help ensure me i can get into the program because i want to do this. also are there any side effects to oncology? cause i am wanting to have children one day and do not want to become infertal or anything.... please help me.