Replaced factory temp gauge with another one.......

Well like you say, the 13 volts went to all the gauges, so the fuel gauge could also be smoked. Did your car have the IVR built into the fuel gauge?

I bought an extra used gauge panel, and the resistance across my gauge coil is about 23 ohms. I'm not sure this is factory correct. But if the resistance across your gauge is very high or very low, then you might have a problem.