It was back in December 2018 that I have mine repaired, but I believe it was around 150$. The coiled wires around circuit board on mine were damaged. He wasn't able to fix the fuel light at the time because he didn't have the correct Thermistor information. All he was able to get was the ford unit as described below, but ford's operate on a much lower voltage so they overheat and burn up in a Datsun.
Disclaimer: Below is what I did, if you choose to do the same or similar thing it is at your own risk. Remember that fuel and it's fumes are flammable and dangerous!
My gauge light "canister" on the sender was shot, so I bought a ford unit (I tested the fords away from the fuel and it's thermistor was too low of voltage, it burned up on the Datsun so DO NOT have it around fuel and plug it in!) , I opened up the canister and replaced it with this thermistor below, it's been working great since December 2018. Test your new Thermistor setup thoroughly before installing it into your tank just to be sure that it doesn't over heat and works properly.
I sent my Thermistor info to Bob's Speedometer, so he maybe able to fix the light in house now.
DESC: THERMISTOR NTC 1KOHM 3972K DISC
Amphenol Advanced Sensors / RL2004-582-97-D1
Ford Canister:
https://secure.cougarpartscatalog.com/fm-ef008a.html