Thank you so much for your input (and encouragement). My DH picked up the 401A for me this morning, and when I saw it, I felt gut-punched. It was filthy and covered with grime. The online pictures were a little blurry, but the seller assured me it was clean, just "hadn't been used in a while".
But I'm not giving up on this beauty. She's clearly been through a lot, and I've spent the day gently cleaning her up, inside and out. Thank you for posting threads to consult! There is a little rattle in the bobbin case, but I will continue to work on her and research. There is also a bit of "mechanical" smell when I sew. Regardless, I believe she has more life to give - and I have great hope for her next chapter! The beautiful thing about these machines is that they are (mostly) built like a battleship, and parts can be replaced if necessary. Thank you again as I embark on this "rescue, recover, and rehabilitate" mission! ha.