My wife's '96 C280 has been afflicted with the erratic fuel gage syndrome. It seems to happen with several different brands of gasoline, although I am now placing her on a strict diet of Exxon Premium for the next few tanks, just to see if it clears up. If it is not caused by the fuel, how do I go about replacing the sending units? (I think that there are two?) Does anyone that has done this in the past have advice to offer? Thanks.