Best used truck for a college student?

I currently drive a 2003 Ford Sport Trac Adrenalin. The truck itself is gorgeous, I have maintained her well and treat her well. However, it's powertrain does not return the favor. I religiously maintain all fluids and keep up on maintenance yet it still seems to break down. I bought this vehicle with 52K miles for $7900 and have put about $4000 into it in repairs in less than an year. It averages around 16-17 MPGs on the highway and 11-13 in the city. Due to my location, I drive around 300 miles a week going back and forth to the university, work, and back home. I also work construction on the weekends so I occasionally need to haul a trailer or weight under 1000 pounds, which my truck can barely handle. I need something under 12K that is extremely reliable and will get me through three more years of college without having to lift the truck every weekend. Payments over $300 a month would be stretching it. Something that doesn't get F-450 like gas mileage would be nice.

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