You will not find an exact wiring plan in any of the manuals. But there are some standards. all of the 12 volt
wiring runs down the center of the coach and then branches off to the sides to the individual fixtures. This wire is in a bundle that normally is under the center roof sheet and attached to the roadside rib. The wire is held to the rib with clips and is quite often bundled with grey cloth duct tape.
That answers the pull it thru question.
If you wist to access the main bundle and replce wires to fixtures you can use the wire that drops down from the bundle to pull a new wire up to the bundle. This does require acces to the wire bundle by pulling the center sheet out of the trailer.
Now, how bad are the shorts, are they where they can be repaired without major surgery?