Cost is going to depend on the installation charges and here in the mid-South I can get them set up for $250 by a local guy that is really good at it. Would suggest you guy the gears Yukon, grab a master install kit (make sure it has quality bearings like Timken), would highly recommend a solid pinion bearing spacer, and then take it to a local shop that knows how to set them up. See if anyone on here from the NE knows of a good shop that is close to you.
Yukon Gear 8.8 gear sets:
I really like the kits from Ratech and their solid pinion spacer.
You should also look at rebuilding the trac-lok while you are in it and get a good set of clutches. Would recomend the Ford Performance Parts M-4700-C kit and order an extra bottle of friction modifier if the gear oil you use does not already have it in it.