Fuel Level Sensor

I have an IP 31 that has a malfunctioning fuel level sensor. The gauge always reads full.
Disconnecting the sensor brings the gauge reading to empty.
I'd like to replace the fuel level sensor but there is only about 3" above the tank to extract it and the senders that I have looked at all extend to the bottom of the tank. It appears that there is a possibility of drilling a hole below the helmsman's seat that would be concealed if the sensor can be tilted aft far enough to get it out. Otherwise, the only solution that I see is to cut a hole in cockpit sole and glass the cutout back in once the sensor is replaced.

Has anyone else had experience with replacing that sensor?

Unfortunately there is no clearance to remove/replace the fuel sensor with the tank in place.
I have a 1987 IP31 that years ago I had to remove the fuel tank to repair a tiny leak on the bottom of the tank.
In brief - drain fuel tank, cut an access in the Port locker bulkhead next to the tank and move the tank into the Port lazerrette.
The tank will not fit through the locker hatch but there is room for you and the tank in the locker to work.
Once I had the tank in the locker I was able to repair the tiny hole in the bottom of the tank as well as thoroughly clean the tank.
Wow what junk came out! With the tank in the locker it will be quite easy to remove the sending unit and clean/replace as needed.
Reassemble the tank and bulk head and you are good to go. No holes in the cockpit floor.

Thanks for your response. It is very helpful. While mulling over the problem squatting in the cockpit locker, I thought about removing the bulkhead but did not know whether the tank was held in place by any other retainers. My IP 31 is a 1986, so it should be nearly identical to the one you dealt with. Since The port cockpit locker is accessible because we are in the process of cleaning and checking all of the components on the boat prior to re-commissioning..