Fuel gauge has stopped working

Hi recently bought a landrover discovery 3 tdv6 hse luxury 2.7 on a 56 fuel gauge does not work so not sure what fuel is left in just have to go off miles we have done and keep topping up, was told its been remapped but don't have proof but going off the performance it's like a rocket . Also has an issue with a slight judder when u pull away or light acceleration if u floor her or use the cruise control she dsnt do the judder. Its a 56 plate so any help or suggestions would be great please be kind don't want to put £££££s into things that don't need done.