I have a 99` Mercedes Benz clk320 & my gas gauge went out. Gas gauge says empty

This is something you can do yourself. You probably just have a faulty gas tank sending unit – there is a float in your gas tank that floats down as the fuel level drops. As the float goes down, the metal contact attached to it slides down a variable resistor. And the contact's point on that resistor tells your gas gauge how much fuel is left. Your gauge is confused, thinking empty is half full and vice versa. You need to get a gas can and fill it up. Then, let the car run out of gas, while it's running. Next, restart your car by refilling your car with the gas can -- this should reset your gauge. Note: with the exception of a very small number of cars, the fuel pump could be damaged by running the tank empty, but you won't hurt anything by going to empty.