"Barhymus"....Your coach has a Centroid sending unit http://www.centroidproducts.com/moncal.htm
. It's unusual for one of these to quit completely. Often, Monaco will run two items off of one fuse, as an example, radio and fuel gauge, but only list the radio on the fuse panel. You may have to go through all of the fuses in the run bay, under the driver's window, and check. Pep Boys and other auto stores sell a small fuse tester that has two pins on one end that are adjustable for various size fuses that allow you to test the fuse while it's still in place. A volt meter set on OHMS or buzzer next to the OHMS setting will also work.
If it's not a fuse, you need to check the sending unit. It's located on the top of your tank on the driver's side. You have a fuel door built into the bay door on the driver's side that can be opened. On the bottom of the bay door are two screws, remove the screws and lift the bay door up and use a prop to support it.
About 18" into the bay, you'll see the sending unit on the top of the tank. It's about three inches in diameter. It has hoses and wires going to the top of it. Check the wires and make sure they're all connected. You would be well served to loosen and clean them.
The sending unit also has adjustment screws on the top to set the full and empty marks. As with a lot of Monaco stuff, the sending unit may have undercoating sprayed all over it and will nedd to be cleaned off.
I attached the Centroid information sheet. If you reach a dead end, you can call Centroid. They've been very helpful in the past. The good news, if you need a new unit (which I doubt), it can be replaced without dropping the tank.