You should be able to do it yourself. The first thing to do is mark where the nut is-- in relation to the pinion shaft. A center punch will work.
Now remove the the yoke [balancer] and seal. reinstall and tighten the nut to the exact place where the nut was before-- a tiny bit tighter will be OK, but never less than before. You can check the rotating force before and after with a dial torque wrench.
People mess up doing this-- by using a impact wrench and over tighten, or under tighten the nut. The torque on the nut, loads the pinion bearings.
Chevy 04.5 LLY, 2X, shell, XDR, MikeL Heavy duty up-grade, 6spd, TransGo, deep pan, de-badged, 65 Gallon replacement Aero tank, LBZ-mp, Kennedy pump, shimmed, Pre-fuel filter, tow mirrors, BU cam, gauges, GPS, Sirius, bags, custom grille, fender vents, HD trans cooler- Curt front hitch, footwell lights, load lights, Studs, head gaskets.--- Jerry