As long as the insulation isn't cracked or frayed where the wire is showing you're probably safe to plug it in. Got pictures?
I don't own a handcrank yet but I find myself constantly turning the handwheel when I need more control. I'm seriously considering converting a couple of my machines to handcranks for just that reason.
Reproduction handcranks are available as well as new wire sets at Sew-Classic.com. If you want to maintain the original look of the machine cloth-covered wire is available at Sundial Wire.
Rodney