If you're in college why are you on the high school subforum?
Anyways, corpsman are enlisted equivalents of paramedics. They aren't doctors, even though they're usually called "doc" by the folks they take care of. If you are interested in becoming one, the Navy will teach you everything you need to know, and you could've enlisted straight out of high school if you wanted. If you want to be "on the front lines" then corpsman are as close to the action as you're going to get. I think most enlistments run 4 years of active duty.
Naval nurses and physicians are officers. In order to become one you've got to first be accepted to med school/nursing school, and then apply for a scholarship, or you go through med school and then just join up after you're done. Doctors in the military do the same as doctors in the civilian world, rely on corpsmen (paramedics) to stabilize in the field and bring the patient to a central facility with the equipment to continue further intervention. To keep things simple, if the Navy pays for your school, you'll owe them at least 4 years of active duty after residency.
I suggest heading over to the military subforum and reading up here on this site
http://www.militarygme.org/ about being a physician. You can also ask a Navy recruiter to put you in contact with a corpsman.
