1997 Lumina Fuel Gauge

1997 Lumina LS 3.1l. Looking for some input on my fuel gauge problem. Gauge had been working fine and then started going to full when tank reachs about 1/4 mark. Once filled up gauge works again until reaching 1/4 tank and back to full. See the sender is on the fuel pump in tank. Any input if it appears to be a sender or what you have seen in simialr scenarios? Also see conflicting info if I must drop the tank or not to repair. Any advice is appreciated.
Thanks!

Typical fuel sender problem.......as for dropping the tank, remove the carpetting in the trunk near the back seat.....between the spare wheel well and the back seat, see if there is an oval aluminum shaped plate ....if there is, remove it.......the pump is underneath it and the tank doesn't have to be dropped....