Winno6-
There are many posts on iRV2 concerning the various locations of fuse panels in the Winnebago/Itasca diesel coaches.
Here is a link to the result of a Google search for iRV2 posts containing the terms "Freightliner," "fuse" and "location."
Here is a link to the same search with the additional term "trailer."
One or more of these posts should help you find the fuse panel for the tail lights.