your in the same boat as me, except i am 22 years old coming out of college. It's nice you are starting young. Most boxing clubs/gyms are very helpful and nice, just go to one and let them know you are interested in joining and they shall give you all the details, when they train, have classes, etc. As for now you could start with the dieting, eating healthier whole foods, and do the alternating workouts with different types of cardios on diferent days. Other guys on the forum would probably have better specific workout plans.

good luck!