Keep an eye on craigsllist and ZW classifieds where there just was an ARB for the rear for $500 (which I would have bought, if I wasn't sleeping). Lockers set up right are OK for the rear, but an ARB up front is just totally awesome, and they work better than stock even unlocked.
Unless you know what you are doing, at least take the differential to a shop, and have them set it up for you. If not set up right, they do not work right, you won't be happy, they wear the gears wrong, it starts to whine, you won't be happy, and they do not work right. Or, you could be lucky (or talented).