$2000?!?! no-no-no, well it all depends on what you know or who you know. Go to an autoparts store, buy a "Chiltons" or "haynes" manual. These vehicle manuals are "tear down manuals" meaning they contain pretty much all of teh info to completely rip ur wehicle apart, then put itall back together properly.
FIrst-Isolate the problem. HOw sure are you that its your rear end? Does it ahappen in all of teh gears through teh ranges in the tranny? What about when tranny coasts in nuetral? If teh noise occurs even when in nuetral it would point me towrds the rear end def being the culprit. Or as i think you said, you can def hear its coming from back tehre.
-pull the cover off of the rear end. Be ready to catch the gear oil in a pan. Do not reuse this. As the oil drains, put a screen or fine mesh over your oil pan the oil is drianing into to catch any metal chucks so you can more easily identify whast broken.
-Then raise the rear end of teh vehicle off of teh ground (properly w/ jack stands). Put tranny in nuetral rotate rear wheels with hands (engine off). You should be able to see whats going on in the pumpkin (rear diff. From what you say, i bet you will blatently see some missing/ broken teeth off of the ring/ pinion. I dont kwo what the rear end is like on ur vehicle, it could be a spider gear set up like my jeep XJ, but nonetheless, you shoudl see teh prob.
- then its as simple as replacing whats broken, haha jk, its not always that simple to replace. Consider your abilities, time ect. I dont kwo how hard parts are to find for that, you might hav eto go to an import car parts place. Try junk yards too.
Hop ethis helped a bit, sorry fo rteh vagueness, but dont let some shady mechanic screw you over and charger an arm and a leg.