When the balancer fails it does so in a very big way, and quickly.
My wife heard a "whomping" in the engine compartment for about 10 minutes, the amount of time for her to get home.
In stop and go traffic, the car was difficult to drive, stalling at times. Too late... the damage was done. Fortunately the balancer only scored/scratched the timing chain cover. If the car was driven for any longer it would have gone through the timing chain cover! An engine rebuild would have been needed.
I'm not a mechanic but I believe the front of the engine would have to come apart and the upper and lower oil pans would have to come off/possibly be replaced. At the time the vehicle only had 50,000 miles on the odometer.
It's a fast fix, and cheap too. The whole thing, parts and labor, was about $400. Not much for a piece of mind.