The two most common failures in the fuel sender are leaky floats and the resistance wire being rubbed by the arm that it opens up giving a bad reading. Float replacement is easy, the resistance wire is not. As far as I know there is no direct replacement for the wire, but I've seen the entire resistance wire/flat subassembly replaced with a later version. That keeps the marking on the seal plate, and that's about the extent of restoring.
Jim