Depending how comprehesive a rebuild you go for to do it properly requires some presition tools such as a DTI (dial test indicator) to set the backlash and a selection of shims to adjust the pinion bearing preload just right. Not very expensive, but still not a cheap option if you arn't going to do it very often.
You can remuild diffs without the likes of a DTI and just do it by feel/eye but its not recomended if you want the diff to last as long as it should.
thats all rollox
do marine gearbox's at work like that, and had no issues, and there reving 6-7k all day long
had no problems with any diffs that ive done, lockers on my 90 are perfect, still not a single bit of backlash in them, even after all the reapeated dumping's of the clutch at 2k or more with the lockers in
yer you should use the dti's ect ect
but, you get to know the feel of whats right
even someone who has never done one before could tell whats right and whats wrong