The question was reasonable and the answer is pretty clear. The truck is worth what somebody will pay, but there is a logical range. That range is probably in the $6K neighborhood if properly titled, in good operating condition, and with minimal rust. Think about it like this, if those trucks routinely sold for the unrealistic asking prices you see, you wouldn't have bought that one for the price you paid. There is no real reason to debate the issue either way. Money talks. You will know for sure soon enough if you actually list it for sale.
Maybe you can get more, maybe less. To be safe, list it on the higher end of the "reasonable" range and see how many times your phone rings. At an asking price of $9K, it probably won't ring often, if at all.
In the end, it depends on how badly / quickly you want to sell the truck. If you are in super rush to sell the truck, you might be forced to break even or make a small profit. If you are patient, you might find somebody who wants to pay a premium price, but I doubt that price will be anywhere near the $9k-$13K price you referenced. With fuel at $4/gal, and with a depressed economy, your pool of buyers is pretty small.
Good luck with the truck, I hope you do well on your deal. Just be realistic in your expectations. At your purchase price, there isn't much to be worried about if you got a good truck.