the starter gets its ground from being bolted to the engine. There are only 2 wires that go to the starter one is a positive battery cable and the other is the solenoid wire coming from the starter relay.
What exactly do You mean by power plug? Just the terminal or power wire as well? Here in Canada I'd just go to Canadian tire or Napa. I'm sure in the US you could go to an auto zone or napa or some car parts store. Hope this helps!!I guess the ground id good, what i need is the power plug from the battery. Does anyone know how or where to get one?