Billybolt,
The wire would only be ruined if it is broken!! The gauge should have two wires going to it I think, one power wire, and the wire to the sending unit. If you have voltage to the power wire when you turn on the switch, half your battle is won.
The other wire on the back of the gauge, (the bent one) as you state, goes to the sending unit. The sender is a variable ground. If you put a wire from that terminal (on the gauge) to ground with the key on, the switch should do something...peg at hot, or peg at cold. This proves the gauge is good, and the wire to sender is defunct, or sender is NFG. This IS a electric gauge isn't it? That wire isn't a capillary tube is it?
Stuart
