Where is the back up light switch mine went out and i need to replace it. its on a 2000 mitsubishi eclipse

The reverse light switch will be on your transmission, mst likely near your shift linkage. It will look like large fitting with a hex head for a wrench to fit on and two wires with a plug coming out of the top. When you take this out, it will have a metal ball on the end that was in the transmission. Before removing it though, you may want to put a jumper wire across the two wires that plug into it and check the reverse lights. If they come on then, it is the switch, if not, you have a problem somewhere else. Let me know if this helps :)