OK so my cousin tried to install a radio but he couldn't so he put the original back in and he didn't use any wire harness so i'm guessing he just cut the wires and when he put it back together he didn't have any electrical tape. I go to try and start it and ill i see is the security light on the battery light on and the low fuel light on. The fuel gauge doesn't move and i know it has gas in it. also the radio doesn't come on. When i try to start it nothing happens but the headlights flash. The mechanic told me that he probably touch the negative and positive wires and that would mess up the whole cars electrical system but i know that the security system is ran by the radio so i really don't know what it is. Does anybody know whats wrong and how much it might cost to fix?