Any idea of the actual procedure that was used to replace the gears? Was the cam removed for the aluminum cam gear? Do you know if they pulled the pan to use a pinch bar on the crank while they hammered the crank gear on (assuming they installed a new gear), or did they drill the crank snout for a bolt and use a regular gear installer? I ask this because its not all that difficult to mess up a marginal crank thrust main bearing by hammering on a gear or the balancer, unless you are stabilizing the crank forward so that it does not get pounded back into the thrust bearing.

Mike