As previous post indicated, sometimes the problem is just a dirty, corroded connector in which case you don't need to pull the sensor, just clean up the plug. If the connector is corroded and original it may break apart when you take it off. A replacement electrical connector is available from the dealer for a couple of dollors. It's claimshelll design - you just open it up to take the wires out and then put the wires back into the new one.

Of course the problem could be the sensor in which case you have to remove and replace. This requires siphoning (with a siphon pump or turkey baster) the tank to a level below the sensor. There is another method of detaching the tank and turning it on its side, sensor up, but siphoning seems to me easier. Then you have to remove a little clip and pull the sensor out. The sensor itself is only $12 to $15 so if you go to all this trouble you might as well put a new one in. It comes with new o-rings which are less likely to leak.