Hey, Ive just gone through the whole process a few months ago. I m currently enlisted in the mlitary also (Navy), so maybe I can help out some.
If you already recieved a presidential nomination, then you have a really, really good chance of getting in. I think he can only give a few out every year (or maybe its just one) Anyway - Being in the military and applying has its advantage too. They dont put you in the same stack as all the civilians that apply, so it gets that extra attention. At my command my CCC auctually flew up to USNA and talk to the admissions board (along with about 15 other applications) trying to get us all accepted. Being military also increases your chances of getting accepted to NAPS (mainly athletes and military personel attend there).
As for the application... its getting REALLY late in the game for that. There are 2 times that the admission boards decide on who they will accept. One is the end of December, the other is Mid March. Im not sure on the app. deadline for march, but I assume it is really soon. Make sure you spend time on your essay. I auctually spent about 2 weeks working on mine, then sent it to a professor at Harvard to have it reviewed... Its what really lets them know who your are, and not just what you have accomplished (they have thousands of exceptional, qualified applicants; the essays are ment to find out if you are the ideal candidate).
Your performance while enlisted plays a really big role as well. I'll give you my example: I graduated highschool with a 3.58 GPA, then dropped out of college with a 2.8 GPA. I didnt play any sports, and did not do anything exceptional in highschool. I ended up joining the military after dropping out, and thats when i decided to turn my life around. I ended getting top of my class in 'A' School then became class leader and ranked 7 of 350 in my next phase of training. All my instructors give me all the top rating on the USNA reviews, and the CO put in his reccomendation for me as well. I got my acceptance letter a few days before Christmas.
I hope this helped. Feel free to ask any questions, or email me. I hope to see you there in July! GO NAVY!