How do you change a speed sensor on a 1998 Aurora?

there are 4 speed sensors in each wheel hub that detect the wheel speed to correlate with your abs or traction control.... if any of the sensors are defective or nonop your light will come on on the dash and the abs or traction control may not work properly. i got quoted 600$ to repair the lr on my 96 aurora,, so i am trying to get the instructions on how to do it myself. so if you find out let me know,,,, randy there are 4 speed sensors in each wheel hub that detect the wheel speed to correlate with your abs or traction control.... if any of the sensors are defective or nonop your light will come on on the dash and the abs or traction control may not work properly. i got quoted 600$ to repair the lr on my 96 aurora,, so i am trying to get the instructions on how to do it myself. so if you find out let me know,,,, randy