Well, I don't have good news to report...
I got the replacement belt in, but it seems my measurements were incorrect... the belt's tooth spacing seems to be in inches, not mm. The belt didn't line up well on the pulleys. Since both are damaged I was looking into finding replacements. The one on the drive motor has 20 teeth.
Some more info about the drive motor: It's actually a DC motor, not a stepper motor. It has a glass graticule on the back and an encoder to sense rotation. Unfortunately as I was working on the motor I broke the graticule :(
Not sure what I'll do at this point... the teeth on the graticule are so fine I'm not sure how I could get a replacement. Quite a disappointment. It took me quite a while to find one of these printers in the first place. I guess I'll keep my eyes peeled for another one or some other qume printer I could possibly rob the part from.
Thanks,
-Jason