Get the box and run it under your trailer, and find a hole for it. I'd also seal up that hold where it goes in the box. Directron in TX has Gig-E switches for $25. I'd also look for some high-end cables (nothing Best Buy would carry) with a strong outer jacket so that it's harder for critters to chew into it (
http://www.turck-usa.com/illustrations/B3026_J20.pdf).
Better yet, get a second router, run DD-WRT on it, and run it in the trailer so you don't have to have wires all over the place.