Changing the spur gear (on the X) is as simple as removing the top part of the trans case; remove the top two screws on each side that hold the black roll bar on, and the top two screws on the case (look at it from the top down, you'll see 'em). Next, give it a gentle lift, and it should come right out.
Now, as for removing the motor; Remove the exhaust pipe, unhook the throttle linkage, remove the fuel tank, (and the roll cage, if so equipped). Then flip the truck over and remove the four 3MM hex screws that pass thru the purple plate into the mounts.
The X 4.6 is a great truck; it comes with all the good parts, as well as a great engine.