That does seem like a lot of money, with no info on symptoms or why they think it's "not working", as marko said.
Your water heater is a Suburban LP 6 gallon model, from the 2001 Roadtrek brochure, which can be downloaded for free from here
You might also find other useful info about your model year by downloading the free owner's manual from here.
Your water heater model appears to be a Suburbam SW6D DSI direct spark model, which means when it's full of water, and there is sufficient propane available from your main propane tank, and the battery is charged, flipping the water heater switch on should cause an ignition routine (you may even be able to hear the clicking of the igniter if the switch is near the water heater itself in the van's layout. My w/h is the same as yours, and I can hear mine if there isn't too much background noise.
Before you spend that money, double check what they told you. It takes a few steps as follows.
Check that there aren't any visible problems at the burner on the outside if the van. You should be able to remove the access cover and venting screen - it's located just forward of the driver's side rear wheel. Have a look inside there, and see if there are any obvious problems or debris that might be blocking the burner tube and/or a problem (loose/unconnected wires?) with the igniter board and wiring. If it looks like there's no debris present and the wiring looks like it's all connected, go to next step. There should also be a large 1 1/16" hex bolt head which is the end of the anode rod screwed into the lower side of the actual tank. It will be obvious if it's there.
Is there propane in the main tank? Check the gauge. It's probably behind the faux license plate at the back bumper. You'll figure out how to remove the cover, to see the gauge.
Is the valve that sends the propane to the appliances open? It's near the gauge you just looked at. Turning it counterclockwise is usually open/on. Clockwise, closed/off.
Is the battery enable/disable switch enabled? Find it on the Monitor Panel that shows battery charge, fluid tanks status, propane tank status. It's near/above and to the right of the side doors. There's a picture in the Owner's Manual.
Is/are the coach battery/batteries charged? Use a multimeter to check them at the battery(ies), or press the "test" button on the Monitor Panel with the battery enable switch enabled.
Making sure there is water in the tank (it is definitely NOT a good idea to turn on an empty water heater) by filling the fresh water system, and making sure the water heater is NOT in winter/bypass mode (see the owners manual pictures), you can try the Water Heater switch above the galley counter. If you don't hear the clicking of the igniter, or the switch doesn't stay glowing red, you may require service.
I would start by reviewing the pictures and appropriate sections of the owner's manual. A little reading and googling can sometimes go a long way to saving you some money.
Let us know how you make out.