How should I exercise and diet for the marine exam?

I did incredibly high on my ASVAB and quite literally every branch has been dying for me, however the Marine recruiter won me over with his character and information about the NROTC scholorship. However in order to p the physical exam i need to move my pull ups from 2 to 20 by Halloween Day. Is this possible in such a short time? and if so how? Also i kinda let my weight drift a little and im in the 190s, i can still run cross country very succusfull but i wanna slim down for better overall shape. What's a good dietary plan i should follow? IF it helps im five foot ten and seventeen.