I attended last year's AIM 2018.
It will be a very fun experience. Before AIM, I ran a lot, did lots of pushups and ab workouts. I also ran during the day (around 1PM or 2 PM) to prep me for the high temperatures.
You can't really train mentally. You just have to experience that during the program. You will be immerse into a lot of yelling, fast showering, moving with a purpose, running hills/stairs and many more. You will see your shipmates struggle with you. The best thing about that is you get to meet people with the same ambitions and goals just like you. You will also have friendships that will last forever. My shipmates and I made a group chat and we are still in contact up until now. Some of my friends decided to attend civilian colleges and most of us like me continued to pursue our dreams of attending a service academy.
Overall, you will have fun for sure. The preparation for the PFE is very simple. I advice to run hills, do lots of sprint workouts and train to run fast comfortably. Do lots of ab workouts that you can find online and train for the cadence pushup. You can't just bang out pushups in the PFE. They will tell you when to go up or down while counting for you.
I know you will have fun throughout this program. New London is beautiful! Good luck to you!!