Please Help me with this decision for my 2002 Ford Explorer....?

[(SOLDIER)]

Hello, I just had my 2002 Ford Explorer transmission go on me. I bought it from a private seller so no warranty and only had it 2 months. I need help with deciding what to do. Should I buy a new car so the rebates cover my "upside down on my loan" or should i just fix it. by the way i owe $7000 left on it and the transmission cost $3500 to replace. Im in the military and could pay for a new vehicle if i decided to stay in but i plan on getting out in a year. So please just put a (what you would do) answer. thanks