The '90 Jetta seems a bit old to have antilock brakes. I understand  if the
fluid in a vehicle equipped with antilock brakes is not changed often,the
antilock unit goes kaput. Very expensive. Another part to consider in  drum
rear brake repair includes a backing plate.Dont know about the Jetta, but
the labor to replace this  is not usually too bad. Some vehicles need lots
of work to replace it. Remember , the shop charges about double for the
parts as compared to our vendors.Still,the bill seems way out of line from
usual and customary charges.