This unit is no longer putting out any heat. Light is on at the front. Inside wiring shows a slight burn on one wire connected to a round circuit ( slides into slot against fin ), what is tis part and can I replace it - assuming this is the problem

The burn means the unit likely shorted out and it could be a multitude of causes. Without seeing what exactly is damaged, there's no way to tell if it's something that can be replaced. You'd be better off returning the unit if it's still under warranty or replacing the unit entirely to be safe.