The front sensors are $156 and the rear is $118 MB list prices. They should be available for a little less.
We seem to get more right front than left fronts and the fronts in general more often than the rear.
You might try cleaning the fronts if you can get them out without destroying them. They are magnetic and can accumulate metal from the brakes.
When the light is on the ABS is inactive. The brakes should work as well as any US 500SEL without ABS. In other words the hydraulic brakes should be normal.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician
[This message has been edited by stevebfl (edited 04-19-2000).]