Gink5

Same as above

aero3685

The output spacers... yeah you need for both sides obviously.

As far as the axle, here is a little test that I have found useful before..

grab the axle shaft, and try to rotate it. See if it rotates even just the tiniest bit while the ends of the axle stay in place. (hold the inner part, and rotate shaft.. if there is play between those parts, or the shaft and the outer one, then that is most likely causing your vibration.)

If you have the money, you may just want to replace both axles, and get the spacers at the same time. Or if you do have one axle with a problem, replace it, and add in the spacers on both.