The entire chassis/amp comes out through the front opening of the cabinet. There was no need to remove any control knobs.
There is some old paper label stuck on the faceplate, and so this is a good opportunity to remove it. It's soaking in a good coating layer of "Goo Gone" solvent now.
My project is to replace the 2-wire ungrounded electrical cord with a 3-wire, grounded cord. I'll post photos when I finish.