Just got word from my mechanic that the seal between the transmission and the differential is leaking. I'm told this is a $600 job, as the transmission needs to be pulled. Does this sound like a reasonable and customary charge for such a service? It's beyond my capabilities, so I'm at the mercy of this mechanic. The leak seems to be small, so I'm halfway tempted to leave it for awhile, perhaps just topping off the differential fluid as needed. I'm driving less than 4000 miles per year, and this is an expensive little repair that was unexpected to say the least. Vehicle is an 89, auto westy.

Thanks,

Troy