Definitely measure the ring and pinion gap prior to disassembly. You want them to be reinstalled at this setting because they wear as a pair. If you reinstall to factory settings you'll end up with rear end noise and possible future damage.
I use white grease when setting up ring and pinions. The prussian blue is okay at best, I think it's crap myself, and is almost impossible for me to read on a new, unworn ring and pinion. White grease was the easiest for my eyes to decipher.
Jeff
