My Tundra was driving like crap. I expected a whole new suspension. Crawled under and noticed a sway bar link was broken. $30 for new links and it rides great. Crawled under the firebird to drop the gas tank. Knocked on it a few times and it was bone dry. Put 5 gallons of fresh gas in, it fired right up!
Still have to do an oil change and some other basic tune-up items, but no swapping the tank!