Continuing the Fuel Sending Unit discussion

Hi all, new here. Just bought a 71 Dart Swinger for my son. Fuel gauge isnt working and was wondering if anyone could tell me a good starting point to try to fix this. I'm NOT mechanically inclined but willing to learn. Any good books with complete detailed instructions and illustrations I might wanna pick up? I want to begin slowly restoring it although its in daily driver condition. Thanks in advance :)

Joe