Back when I bought mine in '98, they weren't bad. I think the ARB and install was a grand for the front and the Detroit was 800.
I'm pretty good mechanically but when it comes to setting preload and coast and load on the ring gear, I leave that up to a good, reputable shop. Takes skill I don't have to set it correctly. Already had the 4:10 gears so no ring and pinion change was required.
I kept my manual hubs in the front as well. No point in turning over the output shafts and universals when I don't require it so it's still lock the hubs in front.
One thing to remember about a locked spool is it's fine going straight but you turn the wheel and the front end will bind unless you are in sand or dirt. Hard surfaces and a locker (especially with a loaded truck) can find the weak point in the driveline real fast, usually a universal joint but sometimes a drive hub or wheel output shaft.
When I lock mine, I'm always going slow and always attentive as to the angle of the front wheels and. the truck won't want to turn any. It wants to go straight no matter what.
Still carry my Lewis winch. Sometimes, locked diff's don't cut it.