Update: I spent the afternoon tinkering. Ah, such fun. I adjusted the Cam stitch length, which was set too long. Then I just ran the Green Girl for a while - sometimes without thread, sometimes with thread, just sewing straight lines on cotton fabric. I figure, after being essentially dormant for decades, she must just benefit from some motion!
This is neat, bringing a machine back to life.
Any other tips, please chime in! What to look/listen for?