When I get close on the diet-pi install I will remove the other reference from my router.
You don't have to. All of your LAN clients (if they're DHCP) get their DNS address from the router. If the router is currently pointed to pi-hole in the Docker, that's fine.
On the other hand, if you statically configure just 1 client with the Diet-PI's IP address, as the DNS address, you can test the Diet-PI pi-hole install by simply browsing the net with that client. Then run another test, on the same client, when unbound is installed on the Diet-PI to confirm, whether or not, the entire package is working.