OK, if the bag deployed and the ETR fired, then you also need to replace the crash sensor (it is a one time use item). It is located on the tranny hump, just about below the stereo. You will have to completely pull the center console to access the sensor. The cable from the sensor connects on the right side under the false floor and is the only red connector there. You can use a good sensor from a salvage yard, just be sure the bag hasn't deployed and that the seat belts retract when you pull the out.
As for replacing the ETR's, you will have to pull the interior trim from the "B" pillars, then unbolt the ETR's and withdraw from the pillar. The other end of the belt is bolted to the floor and will have to be unbolted. The complete seat belt assembly will need to be replaced.
Once the sensor, air bag and ETR's are replaced, the SRS light should be out.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.