You dug this whole on your own and you know that. The way you dig yourself out of it is exactly the way you got into it. One step at a time. You stopped going to school, stopped taking care of your car, etc etc. You get yourself out by focusing on one or two things at a time.
Start with yourself and your immediate area around you. Clean yourself up, get a new haircut, shave, etc. Then work on cleaning up your room or wherever it is that you live that you've let get away from you. The reason for this is very simple psychology. If you start looking and acting the part the rest will start to follow. If what you see everyday is disorder and chaos from that life its easy to get back in that rut. If you keep yourself and the stuff around you in good shape, you'll start taking care of other things in your life.
Make a list of all the things you want to do or change. Seriously write all of them down. Put them somewhere you can look at it everyday, like a mirror. Each day wake up and focus on 1 thing...or two things...if that's too much go back to one thing. Today it may be to get your place in order. Tomorrow it may be spending a few hours on your car... Take it a day at a time, and a bite sized chunk at a time.
If you keep thinking of ALL the stuff going on its overwhelming. I know cause I've been there and still digging myself out in some respects with debt. And as far as debt goes I'm very much for the Dave Ramsey approach. (Start by paying off the smallest debt...even if you can only send them $5 a month...slowly pay it off...start with the smallest and work your way around.) Trust me this method works very well. His book is pretty great too btw!
I'd highly recommend getting involved with the church. There is a lot they can help you with by praying for you, offering you guidance, giving you a support group as well.
The military on the other hand, although I think they are great and could definitely help, they do frown on debt and other things. They'd definitely "make you" get your shit together for sure. However, that is signing a "contract" for your life. In the emotional condition you are in I'm not sure that you should sign such a HUGE LIFE ALTERING contract, where you literally belong to the government. Wait a year, and if you still want to join then join.
All prayers and blessing with you.
Jon