i had a aftermarket stereo installed in my 01 cavalier, a couple days later it didn't turn on, im assuming its connected with the fact that my interior light isnt working either, anyone know the problem?
You can't install aftermarket radios in any GM car 2000 and newer. There is a lot of functionality built-into the factory radio that your car will lose once you take the radio out. There is something called a Class-2 communication bus, and it will mess up the communications between other parts of the vehicle. Have you noticed that you've lost your chimes (when the door is open with the key, etc.)? That comes from the radio.
They should have known this, and they had no business installing that into a car that it wouldn't work in.