Timing chain

99 Cavalier Z24 2.4L Automatic, 165,000 KMS.

Timing chain guide failed, engine stalled, timing possibly jumped,
resulting in the engine stall. Engine turns but would not start,
after several attempts to start, engine locked up.
Apparently a timing chain guide got wedged between the chain
and a camshaft sprocket causing the engine to seize.

Garage suggests possible valve damage, thus requirng head removal
for valve /head serviceing.

Very expensive repair if head has to be removed.

Any experiences or information would be greatly be appreciated.

Thanks