I can tell you now that you will not be happy towing that large of a trailer. I have a Rockwood MiniLite that weighs much less and I'm happy but would not want anything heavier or longer. If you decide on gears go with 4:10, guys on the RV forums swear by them making all the difference in the world. Air bags will help but they do not raise your capacities.
The first time mine did it was when my truck was fairly new, it scared the crap out of me so I bought an OBD scanner. I would not worry about it, when it stays on then it can be more serious.
I traded my black ones for chrome from an inmate here. Easy to change and you should find someone willing to swap over in the for sale section. Shipping was under $20.