'99 528i instrument problems #1

[dbell5]

I bought this car used about two years ago, and have no major problems, but a couple of disturbing instrument or control issues have come up.

1) ABS/Traction control fails after some time driving, more quickly in hot weather.
This may have started right after a shop replaced a damaged left front tire, possibly damaging or "disturbing" somehow the wheel speed sensor.
ABS warning light comes on, and the indicator that Trac is off. I feel a slight, very brief vibration in the brake pedal if I happen to be applying them at the time it fails, similar to the action when ABS is functioning on a slippery surface.

Any suggestions? (Other than "see your dealer", please!)
Is a system schematic available on line somewhere?

Thanks!

Dave