If you have no experience setting up gears, bearings, etc. in a differential, I would strongly recommend having an experienced professional do it.
A very mechanically savvy do-it-yourselfer, with the proper specialized tools, and a GOOD (not Chilton's or Haynes) service manual, could probably get it right, after numerous attempts to set all the parameters where they need to be, for a long, trouble free service life.
If this 4Runner is a daily driver, and especially if you don't have the tools and background to do the job at this point in time, it would most likely be an exercise in frustration.
It would be much easier to buy a complete 3rd member, with gears and bearings already set up, and install that in the axle, then going in with no differential rebuilding experience.
I was under the impression that when changing the diff bearings I just needed to pull the yolk cover off unbolt diff and bearings press new bearings on reinstall and makesure I get the pre load right am I missing something.
I'm new here so noob question is 3rd member considered the whole rear end or just the differential.
thanks