Are the multiple cylinder misfires random or isolated to specific cylinders? The first thing that needs to be done is to correct the misfire condition. You might have a vacuum leak or electrical problem causing the misfire.

Crossfires have 4 O2 sensors - 2 per bank of cylinders - 1 upstream of catalytic converter, the 2nd downstream. In a misfire condition, the unburned fuel goes out through the exhaust. The catalytic converter will overheat when inundated with unburned carbon monoxide and hydrocarbons. The overheating can cause the downstream sensors to fail.

In the event the faults were detected in the downstream O2 sensor heater circuits you may discover an even bigger problem once you sort out the misfire issue and replace 02 sensors. Namely, the possibility that all the unburned fuel has overheated and ruined your catalytic converters. In the event that your cats are no good, all would not be lost. As long as you can demonstrate that you didn't disregard what your manual says by continuing to drive the vehicle, the cats are covered up until 80K miles under U.S. emissions laws.