1screech,
That machine is very similar to my Aldens SUZ-2 machine. Internally they are very complex. Oil everything that moves or looks like it should move.
Grease the cam drive gears.
I suggest Tri-Flow oil and grease.
The controls are color coded, when making settings each control has to be set on the same color for it to work right.
Sew-Classic has a technique of using a non-stretchy string or cord to measure the belt size, then she can tell you what belt is closest. The technique for the string is explained on Sew-Classics belt section. My Aldens has a double cogged amber belt on it, no number for me to tell you.
There may be a lever on it to put the machine into stretch stitch mode. You have to move it to make the back and forth feed dog motion.
Sadly I haven't found an owners manual for my machine either.
Once oiled up and cleaned it should sew quite nicely.
Joe