Here are some excerpts from the above sites:
"The notification, Ford Service Campaign 98M01, warned owners that "premature failure of head gaskets could cause engine failure."
"Head-gasket repairs can cost $1,000. But if coolant damages the engine, it may need more serious work, which can cost $3,000 or more."
"What is the head gasket? It seals the top of the engine, or cylinder head, to the bottom of the engine. When it leaks, it can allow coolant to escape. If the coolant leaks inside the engine, or the engine overheats badly, the engine can be destroyed.
What are the symptoms of failure? Ford says the symptoms are persistent and worsening overheating; heavy, white smoke from the tailpipe; a flashing warning light for "low coolant;" and the constant loss of coolant. Some customers also reported that the heater stopped generating heat before the gasket failed."
There is even an example of an engine failing within 10,000 miles after the head gaskets were replaced from the original damage:
"...Then in August 1999 with roughly 77,000 miles on the odometer, a mechanic told her the head gasket was gone and soon she was going to need a new engine, which would be about $3,000.
Edwards didn't have the money for a new engine, so the Sable sat for three months until a friend made some free, stopgap repairs including a new head gasket. That allowed her to drive it another 10,000 miles until May 2000 when the engine died ..."
Also see the following site for a view of the Ford Service Campaign 98M01:
I hope this helps.