I received my 50 AMP Progressive hardwire surge protector a couple of days ago and I'm in the middle of the exact same project.
I plan on removing the wiring from the breaker box and connecting that to the input side of the surge protector and then adding a new piece of wiring from the surge protector to the breaker box.
For other reasons, I did recently remove the outside plug. I reinstalled it with a bit of silicone on the gasket and around the outside of the plug. BTW, the wire on the back of the outside plug was too short to allow me to pull it out more than an inch or two due to a strain relief that had it tied down. I ended up removing the breaker panel box completely so that I could see in behind it to discover what was holding the outside plug.
