Quick update: Success!! After several evenings of rain, it was dry enough lastnight to finish the repairs. Got the wire fished, spliced, and grounded, and viola! Success! All the upper marker lights are working once again. Of course I have to skip town for work for a few days, but i'll have four days to rebuild the tub and surround before we leave next Sunday for a week. The silicone may still be soft, but we'll get it done! Momma says we have to or no trip!
If anyone wants to see how I ran the wire, I have a couple more in my flickr gallery with the rest, just can't share the link from my phone...
Oh, and Jayco was no help. They emailed me a 7 page document of trakler light schematics supposedly for my trailer. Turns out none of them was actually my trailer!!