Rear Differential/Pinion replacement cost?

I have an '88 Supra, manual, and noticed a clunking sound in the rear. It's at the shop and mechanic said it probably is a torn pinion in the rear differential--Does anyone know how much I can expect to pay to have it replaced/fixed?

Thanks for any info.

Are you sure it is from the differential, or could it be coming from the center carrier drive shaft bearing? The carrier bearing problem is very common, the only permanent solution is to upgrade to a one piece driveshaft. If it is the diff then good luck, it is a PITA to remove and install so I'm sure he will charge accordingly. :(

I was told the clunking in my 1988 is a bushing in the rear transaxles. I just left it. That may be your problem. Does anyone know about this?