enlisted to officer nurse

[navy20]

Hi, I am currently enlisted in the navy and I am looking to pick up an officer package to be a nurse. I am trying to figure out what my best option is to get my degree and wondering if anybody has any advice. Is it possible to start going back to school while finishing out my contract? I originally wanted to be an army nurse and don't how to switch branches and switch to officer? I wanted to join the army because I thought there would be more trauma care which is what I am interested in but I heard the navy has a fair amount with the marines. What is the quickest way to start this process? I know there is a lot of questions but any advice and suggestions would be appreciated. Thanks