Fortunately the throat plate lever on this machine worked perfectly so it just popped right off. The feed dogs came out readily, as well. But I did not know how to remove the bobbin case. I guess I did not do it on the 401 when I cleaned her out, or else, I forgot. That would not surprise me.
I referred to the 401 manual. To remove the bobbin case, all you have to do is slip the position bracket to the right and lift out the bobbin case.
I did that and cleaned and scrubbed and scraped all the crud out from in and around the hook. But I left that hook alone. I never noticed that piece of red lint in the bobbin case. These photos really magnify detail. I did notice it when I was cleaning the bobbin case:
I imagine the machine would not have stitched well with that lint trapped in there.
I am now the lucky "winner" of a manual and some accessories for the 403. Stayed up to watch the countdown on eBay. Now I can go to bed.