well you won't rebuild the original locker your swapping out the unit as a whole so you just need ring, pinion, new bolts and washers for the ring gear.
then you will need to adjust the spacer and the lash between the gears. you will need a set of shims if you have a 9" for the pinion support.
since your inside the pumpkin you would want to inspect the bearings. Now if the new locker unit has a different Inner diameter bearing then the original rear then you will need new bearings. or if the bearings have rust pits in them they should be replaced. what you will need will depend on any damage you find when you take it apart. you want to inspect all the bearing surfaces and chases for defects.
if you were rebuilding the original locker then you would need a shim and clutch pack, new thrust washers and pins,,, etc....
it is possible to find unseen damage to the splines or the wheel bearing seal surface that may require new axles.