i have a1999 grand prix gt. after replacing the water pump and manifold gaskets my gas gauge quit working. the low fuel light stays on as well what do i do and how do i access what youre telling me to

Remove the fuel tank and replace the fuel sending unit. Does the gauge move if its on full? Do you know the approximate gas mileage of the vehicle? Fill the tank, check the gauge and then do the math of the tank size and run it till its 1/4 tank to make removal easier. I'm not guaranteeing that's the problem but %99.9 of the time it is.

Get the check engine codes read at a parts store. There are over 2000 universal codes that it could possibly be. There is also the possibility that the float on the sending unit in the tank broke so now the arm sits all the way down like the tank is empty.