ring and pinion

[IndianScout]

I'm going to swap out my 2:73;s and put in a set of 3:23 or 3:42's, I've not decided yet. it's a GU2 G80 rearend

when I pull it apart and if I lay out the spacers so that when I put it back together will I still need to get the rear end setup, or should I just take it to a shop and have them do it.

[Code 91]

you may get away with eyeballing the pinion depth spacer, but you'll probably need to adjust spacers to set your backlash. Too loose and it may knock, too tight and it'll whine.
You can get a dial indicator tool to measure the backlash, and use the pattering grease to verify your depth and tooth engagement. You also need to consider the pinion bearing pre-load and how you can get the crush sleeve set correctly.
be prepared to replace the pinion shaft lock bolt too. It bolts into the diff and through the pinion. It can be very difficult to remove and can be broken or rounded off if you aren't careful. $5-10 depending on where you go.

If that sounds like too much for you, then take it to somebody else to do it. It's not THAT hard, it's just a bit if a PITA to have to pull it back apart if you do it wrong.