School me please

Is there a proper way to remove the wiring plug connectors from the juntion block? The book calls it the junction block.
The thing I'm talking about is on the passenger side of the cockpit in a 1977 280Z. It's white and right above the ignition transistor.
I'm not talking about the plugs that plug from the cockpit side I got those easily. It's the ones that come from the engine bay side. They have 4 prongs on the back side and were very difficult for me to remove. I know what I did wasn't the proper way.
For the future could some one please tell me the tool to use or the proper way to remove these things. You aren't just susposed to push on them are you?

Another question for the other side. Will the ECU connector and wires fit through the fire wall hole or do you have to take the wires from the engine bay back to the cockpit?

Thanks in advance.