Lowdown on changing pinion seals?

I've tried researching but I've found anwers from just remove, replace, reassemble all the way to tear down the entire axle to accurately check bearing preload. What's the real deal? I've bought new pinion seals and pinion nuts. Now how do I replace the seals without messing anything up?

It depends on what axle your talking about.The D44 Im working on now uses shims to set pre-load,once its been set you torque the nut to 200-220 ft/lbs.On crushsleeve axles you have to apply torque until you reach the pre-load value.on a seal replace on a crushsleeve axle the best you can due is mark the nut and count turns,then re-assemble with the same number turns and match your mark.

Well, I'm refering to a HP30 and an 8.25. The 30 uses shims so I guess that's easy enough with a big torque wrench. The mark and count idea seems okay for the rear but should I tighten it up a little tighter than it was, to account for things loosening up? This would mean the old pinion nut would be reused, I assume that's alright since it isn't a lock nut?