I learned a lot about repairs on one. Here is a service manual link:
http://parts.singerco.com/IPsvcManuals/306W25.pdf
you will have to scroll down 125 pages to find it though.
There is a LOT of information right here on QB - you might need to do an advance search. Several of us on here can tell you how to do that $180 job for nothing but your own labor.
http://www.youtube.com/watch?v=zFE4I..._order&list=UL
http://www.youtube.com/watch?v=4sEr3...eature=related
If you run into any problems please post a pic and some idea what isn't working - we'll try to help.