A productive evening
My Adler Contessa de Luxe now works! It has a lovely font. I cleaned it, changed (respooled) the ribbon, and made a few little adjustments. It still has two problems: one of the sticky keys is still sticky (the others aren't anymore), and the bell doesn't work most of the time. But I'm happy, it's the first machine I actually repaired.
Thanks. I agree with the "worst thing" comment. I can always clean the machine again!