Interior lights won't turn off

It seems like you have a bad door switch. The switch is located in one side or the other of the door post. Using a continuity tester on the terminal end of each switch should show you which one needs to be replaced.You need to determine which one of the wires is the feed and which is the supply. Leaving the supply lead connected, put the ground clip of the connector on a ground and disconnect the feed lead. Put the probe end of the tester on the feed terminal and push the switch in - if it is good, the tester light will go out when the switch tip is depressed. It is not too difficult to replace, but you will need to be careful not to lose either of the wires in the door post - tying them with a piece of string will help to keep them accessible.