Open the trunk and it will be on the trunk lid hinge
Im sure one of your speakers are grounding out. This means that one of your speakers terminals or a stripped worn out wire is touching metal. When this happens, your deck goes into protect mode and shuts off the amp. This would explain why it powers on but has no sound. A less likely problem (but it is very possible) is that your external amp went bad. You may think your car doesnt have one, but it does have a stock amplifier. Im sure it has some sort of amp to power your sound system, pretty much every luxery car does. Considering that its over 10 years old it is very possible.
The cost to fill a gas tank in a van will depend on the rice of gas. The higher the price of gas, the more it will cost to fill the gas tank.
You will need to know how many gallons it takes to fill the tank and the price per gallon of fuel. You do the math.