OH boy is that one purty!
The bobbin winder is probably gummed up due to old oil in the shaft driven by the bobbin tire. I use Tri-Flow oil and pump it full through the little oil hole. Then I let it soak and occasionally turn it. The Tri-Flow oil has a solvent property that will dissolve the old oil and free up the winder.
Taking it off and thoroughly cleaning it won't hurt either. But it's not really necessary.
joe