You've got a Dana 80, the pinion yoke torque is around 450 ft-lbs. Since I'm willing to bet your torque wrench doesn't go that high, scribe a small line on the nut and the shaft before you loosen it, then retorque it to the same (or slightly more) place. That's what I did. My yoke was OK but I did polish the little groove with some 400 grit wet/dry sandpaper.
Oh yeah, you'll need a puller to get the yoke off too. They are a light press fit.
There won't be much (if any) lube loss.