That actually seems to be a common issue with that model year. I would suggest taking it to the dealership, since it has such a long mileage and is relatively new car.
Yep. Toyota trucks are proper gas guzzlers. However, you can still drive economically and increase your mpg. If you driving on the highway, reach your target speed as fast as possible, change to a higher gear and stay there. It won't help much, though. I've been actually thinking about getting...
It depends on where do you intend to drive. If you plan to drive mostly in the city, 4 wheel drive would be pointless. You'd just get a poor mpg. However, if you plan to go off road a lot, 4 wheel drive is the way to go.