I wouldn't be too concerned about the cracked epoxy, but be sure to check the ESR of all electrolytics on that board. Some of them are highly stressed.
Also check the screws that hold the various power semiconductors to their heat sinks, very common to find these loosening up over time due to cold flow in the PCB material. It's a good idea to renew the heat sink compound as well, after cleaning the old stuff thoroughly with alcohol.