On FRPP gears I always swap whatever pinion shim is on there over to the new pinion and so far it came into spec everytime as Ford runs a master dimension on gear sets.
I torque up the pinion nut...slowly... and once I like it I throw my indicator inside for "in/out" freeplay....freeplay means sneak up on it a tad more...If you have it TQ'd to spec, no freeplay, and she moves freely with just a light drag, then your there.
If you dont have mucho miles and the bearings and races look fine, no prior noise then leave them alone...don't replace whats not needed. Odds are it'll fall right back into spec.
Ring gear goes right on and TQ it up...carrier shims go back in the same place (make sure you mark which side and where the chamfer is) I use baggies and put bearings, caps & shims per side for re-assy.
Watch out for the small pinion shaft lock bolt...its 5/16 and you can strip the head if not careful..Ford used that badazz Orange loc-tite on it. I use a torch or heat when it gets to feeling funky.
The ABS relucters can be a mofo if they choose to and feel like not moving.
Replace your axle & pinion seals while your in there...cheap money.
As Davis said...you gotta feel comfortable and have the tools to do it...it's cake and youll be amazed how easy it it...long as you use FRPP gears that is.
Seen this write-up ???
8.8 Axle Gear Install