hahahaha....so superK..you took the needle off?
if ya left it factory...it should be relatively accurate..
remember..the fuel is sloshing back in forth in the tank..so the meter is gonna go up and down depending on if you're going uphill or downhill..
what i did..is..i fill up my tank..and i saw that the needle was maybe like...1mm off..
so i open up the clutster and push the needle...freely up..until there is some resistance..
then i just push it 1mm the point where it stopped moving freely
oh yeah...make sure your car is level...now put everything back in and turn the car on..the needle should move to FULL

im not sure about the fuel level sensor..
i heard somewhere that its a plastic container that floats somewhat like the balloon in the toilet resevoir...but over time..the plastic container would leak and fill w/ fuel and sink to the bottom..