If I were you, I would put your C-class in the paper. You should have no problem getting $7,000 for it, perhaps more. And if your dead set on getting a W140 body, look for a 95 or newer model. They were facelifted, not so wide. Just my 2 cents.
Dont ever trade your car in, you will never get anything close to what its truly worth.
93 300D 2.5 Turbo, Black/Palomino 273K
09 E350 Black/Black 41K