[biggbabysweetz1]

i do appoligize first off for posting this so late into the game but anyhoo. ive had the same problem multiple times. 99.9% of the time the connector to the headlight came loose but this doesent appear to be your problem. follow the directions in previous posts for checking voltage. i really dont think your switch went bad, it should (most of the time) give you some warning signs, ie. flickering lights, electrical crackling sounds, etc. for your other question there shouldnt be any problem piggybacking your tail lights into a trailer harness. just make sure when its all said and done your trailer isnt drawing too much juice otherwise it can dim lights on that circuit, AND/OR blow fuses.
typically when you piggyback you wanna replace the tail light fuse with one thats 5 amps higher than the original, just to give your lights a little more breathing room.