Oldsmobile/Buick Repair: fuel guage, olds aurora, fuel guage

Question
1998 Olds Aurora-fuel guage drops to empty after starting and moves to full, then to empty when driving, bouncing between full & empty.   Tank is 7/8 full.  Appears to work better after 10 min, but is erratic at times.  Does tank have seperate sending unit or is it built into fuel pump?...and do you think its the sending unit?
                   Thanks, Larry

Answer
hi larry.in answer to your question yes fuel pump and sender all one part there is an access panel in trunk under carpet on pass side of car near the rear of back seat this is a simple unit to change most anyone can do it.and that is a common prob for this vehicle.and it will work better when it is warmed up.because it works on a potentiometer.same as a light dimmer in your home.hope this helps good luck  billy mac