Your right Wildman. The sensor in the fuel tank is the most common. The little fingers on the sensor corrode away and cause this problem.
The other thing to check is a connector under the van. About right behind the drivers seat under the van is a couple harness connectors that go up into the floorboard. Sometimes they get corrosion (green) and cause the fuel level gauge problem. Be sure to check that before having the gas tank dropped to replace the level sensor.
At the bottom of this page, there is a picture of a Fuel Level Sensor