A balancer should be easy to spot by looking at the face of it. If you see large cracks and can see the outter piece of the balancer move while tugging on the belt, then it'* bad.
Noises behind... the crank sensor isn't going to take much abuse IMO if the rings (3x or 18X) have come loose. In addition the pcm wouldn't know how to interpret the signal from a loose ring and would most likely not run the motor well.
Noises that can be behind the balancer could be a broken chain tensioner, and depending on how loud etc the noise is, possibly a piston rod bearing. Usually low oil pressure accompanies the bad bearing.
00 Regal GS: All kinds of cool stuff.