The extra button on the coin door in mpu200 sterns is a duplicate of the S33 button so you don't even have to open the head.
This will only clear the audit ram - it won't do anything to clear anything else. Usually not an issue, but there can be with the ram used for the sound effects. The only way to clear that would be to run a clear ram rom, or pull the ram out (or the batteries). Battery pull isn't ideal because ram doesn't necessarily come back up 'clear'.