Does anyone know how to repair a vintage sewing machine?

I inherited an old Sears Kenmore Zig Zag sewing machine Model 1802 recently. It was my mom's and it is a very beloved and cherished item. It is one of the only things that was given to me after my mom passed away. It hasn't worked in many years, and I would love to have the chance to use it again as I did when I was young. As far as maintenance goes, we've oiled and cleaned everything we could after referring to the owner's manual. The motor works, the foot pedal works, but the needle and foot pedal are really slow moving. Is there anyone out there that might know a thing or two about this poor old relic? I would certainly appreciate it!