If you're not comfortable with heat, don't mess with it, but as Janey says oil underneath also, and in the nose of the machine, where the needle bar and presser foot bar are. And cycle the machine as you oil to make sure the oil is working it's way into all the joints.
By "spin freely" I mean that the entire machine mechanism should move freely through a cycle by turning the hand wheel, with no sticking or slow spots.
One more remote possibility, that I had come up on a machine, was the feed dogs hitting the needle plate. I would remove the needle plate and see if that affects the movement of the machine.