The market for a truck like yours, especially a 1st gen Tundra, is probably very limited. Not only will it be hard to sell, it will be hard to get a decent price for it.
Since you're already looking at a truck payment, I'd simply keep the Tundra and buy a second truck. You'll get a multiple car discount on your insurance too

A Tacoma sounds like a good choice - not too expensive to buy and will get better gas mileage. Now is a great time to buy, if you're ready. I'd love to be in the market right now without a trade!!!