I always drop the whole shaft. Separating and reinstalling the front and rear parts at the slip joint sounds like it might be a time-saver, never thought of it. If it's good and tight with a good dust boot, you have to remove the zerk fitting to separate or put back together. I would guess it's easier to get the phase lined up right when the whole shaft is out though. Never tried to do that with the front part still bolted to the t-case.
On the insulator - recollection of my daughter's 85 runner was that the x-member bolted to the frame, right? If so, just unbolt it to put in the new mount.