well could be just the bearings, be real hard to tell what kind of condition the gears are in without taking off the diff cover. but as you wanted to know specifcally., youd need a set of carrier bearings a pinion bearing and seal, possibly axle bearings and seals. maybe a ring and pinion gear, maybe a even spider gears. if it went that far id be thinking time to get a posi/tlock and maybe some 3.73 gears. 1500 seems like alot for just bearings. i have a whole new rear end , gears and posi with new bearings, parts and labor about $700.
there probubly quoting everything in the rear end that they can, at full price. i think id get a few more quotes , think about buying the parts online and save a few bucks, expect to only pay $3-400 for labor.