You have a brown panel that has breakers and fuses in it. Open the pop down door, loosen the 2 captive screws, and remove the complete front by lifting and pulling. The bottom half of what you see, is the converter. In this picture is the stock one, removed, but still wired in, and sitting next to it, what I replaced with. It is NOT the one YOU should use.. LOL. It's a deck mount I had laying around after fixing/repairing the factory one in our vintage Airstream.
The converter tray is held in place by two screws at the front, and once the tray is out, the converter is held in place by 4-5 screws through the bottom of the tray. You will have two set of wires to deal with, the 120v supply from the breaker, and the 12v supply to the fuse panel. It's up to you to decide if you want to change out the fuse panel itself to the one that comes with PD converter section.