worth it? well that all depends on if you feel that it's worth it, personally if you have the coin do a 4.0 and 4:10's, for the engine i believe since you have the 3.0 you would have to get a wiring harness, engine, transmission, maybe even drive shaft but not sure. That can all add up quick and then you also have to make sure your 4.0 is in good health before you drop it in and that could mean nothing or it could mean rebuild. Now axle, yea it's easy to do all you gotta do is get the axle/brake lines/u-bolts/ and have someone move the perches or if you are a good welder you could do it yourself, if you have 4 days free you could get it done, and i only say 4 days because you might hit a few snags along the way but most likely not.