Well... looks like youtube helped me find out what the issue likely is. Fast forward to 26:00 in and you'll see the worm gear completely ate up the brass spur gear. Not an easy fix since you can't just order the spur gear. Looks like a whole new transmission is in order if I want to get this thing working again. Looking online these transmissions are going for about $140.
To scrap, or to save? I'm leaning toward scrap at this point, perhaps part out?
Reference replacement transmission #s: 618-04296B 918-04296 618-04296 918-04296A