Navy Nurse Corps vs AF Nurse Corps

Enter "Air Force Navy" in a search on this site and you'll find several posts on this question that may help clarify some of your questions. Also I suggest you talk to recruiters from both branches and even apply to both; it's good to keep your options open.

As far as when to talk start talking to recruiters; if you starting talking to one now you can apply for a program to pay for your education. For instance, the the Navy has the Nurse Candidate Program which will pay you 10,000 (in two $5000 payments) and 1000 a month for up to 24 months if you make a committment of 4 or 5 years (I can't remember which). The Air Force may have a comparable program. If you choose to wait until graduation both branches have pretty good sign-on bonuses and loan repayment programs; if that's what you want to do then you should start applying several months before you graduate to make sure you get everything in order on time (there is a lot of paperwork and recruiters can get very busy). For instance, I'm graduating in December and I'm sending in my application for boards in October and I started the process of applying in May.

There are other people on this board who will be able to answer your other questions more accurately than I can.