Having an issue related to the military. Any advice is appreciated.?

Ok, I'm about to go active duty in the Navy. I ship for basic in 2 months. Now here's my issue. I joined the Navy because of my mom, not because I wanted to. I wanted to join the Marine Corps, and I still do. My mom, ya know how moms are... is afraid of me dying over there. I'm not afraid.. well, let me rephase that, I'm very scared, but I want to fight for my country. My rating in the Navy is YN, so all I would do is paperwork. That's not the way I want to serve my country. I want to discharge from the DEP, get my diploma, and enlist into the Marine Corps. I'm proud of the Navy, I really am, but not as proud as I would be if I were a Marine. This isn't some false bravado issue I'm having, it's just because, I want to fight for my country. If everyone was afraid to die, then our country wouldn't be a free country, cuz nobody would fight for it. I would just like some advice on what I should do here...