ABS Tone Ring and Sensor Locations

Where are these items and how hard are they to diagnose and service. My symptoms are: Cars braking system is fine at each startup/ABS light is off. At first application of the brakes there is a buzzing sound from the engine bay and a vibration felt through the brake pedal/ABS light comes on and stays on. After the first stop with buzzing and vibrating, the noise/vibration is gone and the brakes work fine. (although I doubt I actually have ABS at that point)

Tone ring is behind the hub. Easier to replace the entire hub.
Sensor is the line to the brake and goes to the lower part of hub.
Once you look, you'll see it. There are only two lines there, one is a brake line.
Have you lost a lot of fluid lately?
Bleeding an ABS unit is not something most of us can do, if that is your problem.
Google subaru abs malfunctions and you'll have a starting point.

O.