yup. agree with mike and brad. Definitely the way to go.
Now, be aware, though, that I've heard of guys with auto's doing fine with up to 33's on stock 3.55's, but the loss of power and mpgs are noticable, as are the raised temps if you have to go up hills. Your truck will be fine, though, if you need to run like that for a few weeks before getting to your gears...
(e.g. install lift and tires, and then the next week get gears/lockers done...I'd much rather do it that way, than have super high gears/lockers on tiny wheels. You'd be revving the crap out of your 4.0l..haha. It'd be a tire-spinner, though.)