[A4] lights mean bad module?

[S. C.]

Just purchased '99 A4 1.8t avant w/ 230k miles and always dealer
serviced (until now).  ABS light illuminates, brake light flashes and
intermittent warning tones sound while driving.  Often they stop while
driving and all seems well; sometimes they don't stop until car is
re-started.  Doesn't happen every drive and doesn't seem correlated
with any event.  Dealer told PO the "ABS module" would need replacing
to fix the problem and quoted 700 or so.  Any input?
Freedom, NH Audifan