How much should replacing the flywheel/flex plate cost

What is your question?

Flywheel is cracked. Observable through inspection port. It makes a loud clacking noise which is RPM and load dependent. Car starts and runs but there is a slight lag in acceleration under load (going uphill, driving w/AC on, etc...) Noise not really loud all the time. No noticeable leaks. Belt and tensioner changed recently. Did not make difference in sound. Tensioner rubber center was not damaged, either.

How long has your 2010 Ford Crown Victoria had this problem?

2 weeks