Basically, you call up the new place, say hey I've got a shitty loan, can you beat it? They say yes or no. If it's yes, they basically pay off the old loan, and you pay them now, hopefully with a better interest rate. Might cost a fee, but if you can't sell it right now, then this will at least save you money in interest and lower your monthly payment. You could still pay it down enough to sell it, but it's up to you. Doesn't hurt to call.

I don't know when you can join USAA, but I'd try them. Because they work with service members they can probably get you a better deal, also look at refinancing through them, I think you mentioned a 14% rate? They might be able to beat that, and knowing that you'll have stable income for the next few years makes a difference in rates.

Are you with USAA? Most of their customers are service members and they can advise you as to what to do as far as insurance. When we shipped our car, they had us drop the standard insurance and we only payed a fraction. You could do something similar for the months you're not driving it, during basic and when underway.