New to MFP- I am ready to get back into shape and stop making excuses for myself.

Hello, my name is David. I am 22 and currently a senior, working on my bachelors in music. I hope to teach in highschool or middle school in the future.
However, as of now I would like to join the army when I graduate. (Or at least have the option). I want to have the choice to either join the army or continue on with my education.
In order to do that I need to lose weight. When I turned 21, I started drinking beer and brewing beer with my roommate. Things got out of hand pretty fast, I started drinking more and more and now I have a big beer belly and never have energy. Up until now I have always joked with my friends about being fat... Because I have wide shoulders and am tall my weight has not been very noticeable. Recently my self image has just plumeted and I really need to click restart. I remember the days when I would run 5-6 miles a day and want to get back to that.
I used to play lacrosse in highschool, so I know how to work hard. I just keep getting in my own way, it is time to stop that.
I would appreciate some guidance with my fitness and diet (Diet especially).
Thanks,
David