I would find another dealer. There are 3 or 4 small bulbs that light that panel. If you buy the bulbs from Toyota they come with a socket. They are $3-4 ea. you can buy just the bulb from Radio Shack for $1-2.
It's a five minute job to replace them. Do a search to find the steps to remove...
I agree with Wild Snapper, your truck will do fine. Make sure you have brakes on the trailer and take your time. I find that if I keep my speed below 65 mph. my fuel mileage is in two digits.
It ain't that hard. I suggest you buy an outboard motor lower unit gearoil pump. It fits in most of the gearoil bottles. You just pump the new gearoil in until it overflows.
I used a pump that is designed to change outboard lower unit oil. You can buy them a Walmart, Academey etc. They should be less than $10. and screwed right on the gear oil bottle.
I tow a 22' boat in overdrive. I down shift for the hills. I try to stay around 65 mph (2000 rpm). The truck does a great job.
Make sure you check your tire pressure (max inflation) and lug nuts on the trailer.
My experience is that RP is full of additives while it's base oil is just ok. It's like buying a mediocre steak and putting a lot of A1 to make it taste good. I would rather have a good steak and less sauce.
I suggest you stay with Mobil 1 or Pennsoil synthetic if you want good oil...