There is the little issue that if you regear with ARB's for the 100, that you have to customise the locker using parts form both the 80 and 100 series locker. However I am sure your trusty 4Wheel Parts Whorehouse 18 year old will be able to read that in the application guide and steer you in the right direction.
$5k is pretty close for parts and labor doing a regear and ARB's with wiring, lights on dash (depending on year) and proper switches etc. There are cheaper ways to do it, depending on how detail oriented the customer is. Also, you have to compare apples with apples regarding what parts are all replaced and what is used in their place, ie carrier bearings, pinion bearings etc etc. Also take into account the new axle tube seals for the front etc.
Most shops will charge a flat rate for this work. Some of it is to carry the warrantee. Last thing you want is to pay cheap and then have issues later with a shop that does not stand behind what they did. Pulling a third member for warrantee is not fun or very profitable. And it does happen.
Also, make sure if you buy parts at a different shop from the install shop that you get the same install rate. Jobs are priced on profit on parts and labor. If you loose the profit on parts, you have to make it up somewhere else.
trying to save $200 for a compressor on this size job is not worth it in the overall scheme of things.
One can also buy complete third member set up, but you have to be careful putting them back in the housings not to damage the copper lines etc.
Gear setup is not rocket science, but there is a certain amount of experience needed. Many guys in 4x4 clubs do this regularly for friends and do it for a case of beer. That is all good, just have clear communications before the time as to what is expected when things fail. Obviously the beer route only carries a warrantee equal to the handover period of the beer.
