What's the best way to replace the Cluster Voltage regulator?

You can check the copper traces on the board to make sure they are not shorting anywhere. If they are shorting, I would think the copper should be visibly broken. Have you tried pulling the gauges and plugging it back in to see if the fuse blows? Since it is all one circuit, it could be possible something got knocked loose down stream of the cluster and is touching ground. Pulling the gauges would at least determine if there is an internal short in one of them.