Lucky you! Lots of times on industrial machines the tail of the thread gets pulled back in and then binds the machine. I would first check the bobbin, case and feed dogs in the machine for wrapped thread. My machines are much older but one does have a button on the bed which I think is called the "Safety Clutch Lock" to protect the machine from damage. I have not had to use mine. Make sure you oil the machine first and if it has a clutch motor maybe put grease in it. Most guys know how to do that but newer motors don't need grease so look up your model number.
The bobbin is not wound on the machine but by a separate piece on the right side of the machine with a wheel that leans against the belt. The manuals should help and if not check out any industrial youtube and you will see how to do it.
Here are some links from manuals and I hope they work.
http://parts.singerco.com/IPinstManu...25_535_543.pdf
http://parts.singerco.com/IPinstManu...5_135_143A.pdf
Let us know how everything works. They are well worth the work and frustration.
Have fun,
Lisa