Be sure to buy the GERMAN made supermatic, metal bobbins. Any other bobbin will not work in these. There are a few sellers on ebay that sell the German made ones, and Ray White sells them. Otherwise, you will have tension problems. I would clean off the motor well and there should be a capacitor near it that also should be dried off. If you have to replace the pulley(which you may have to do) the motor would need to come out anyway and you could get a better look. Does the pulley have any flat spots or does it look o.k.?
You can get cords from Sewingparts Online or many other internet sellers. Sew Classic will either have one or order you one. It's a generic cord and will only run you about $12.