My ABS sensor makes the ABS light come on. Is it a cheap fix or not?

I have a 2004 Saturn VUE AWD V6. The ABS light comes on occasionally, and the brakes shudder occasionally. I was told it is just a sensor, since the brakes work fine and were just replaced a year ago. Is fixing the sensor a cheap fix, or am I really going to get taken to the cleaners? (I have a history of "cheap fixes" becoming mive repair bills)