2005 Hyundai Accent Brake and license plate light on hatch

I was recently pulled over because my license plate light and the third brake light in the middle of my back windshield were both out. I replaced the lights for the license plate but they still do not work. The mechanic said their initial guess is that the wiring is broken because there does not seen to be any power current. Do you think this is the case and how much would it cost to re-wire? I'm a girl and don't want to get taken advantage of for being naive about cars.

Thank you!