"ABS" LIGHT ON Where are the Sensors

Well, unless you just want to start buying / switching out sensors, the best place to start is with a code scan. That will tell you what the computer thinks is wrong, and likely pinpoint which sensor is bad (assuming it's a sensor)

With the ABS light on, the brakes will work fine, however there will be NO ABS function at all.

For reference though, the Rear sensor is located on the top of the differential, above the yoke

The front sensors poke through the backing plates of the front wheels, near the center of the spindles.

The rear sensor runs around $20.00, I forget what the front ones run off the top of my head.