1978 Pontiac Bonneville Guages disabled

Hello I have a 1978 Pontiac Bonneville sedan with the 403 motor. The speedometer stays at zero when i'm driving. The odometer does not move, even after I drove several miles the milage was still the same, and the fuel guage always reads empty.I topped off the tank but it still reads empty. Is this kind of problem expensive to repair? Before I take it to the shop I thaught I would post my question here, to see if I could get any tips on how to fix it myself. Any input or advise would be greatly appreciated. Thank you.