Visually the only item that looks a bit different to me is the ABS Unit on the drivers side of the engine. Other than that the body panels and engine look the same. Can you take shots of the interior dashboard. As everyone else has already suggested definitely check the VIN# to determine if it's a 420 with a possible 500 bodypanel conversion.
Also take a picture of the battery in the trunk, the 400E and the 500E have different configurations and this would be an area most people wouldn't think of changing.
02 C32 AMG
84 190E 2.3 5 Spd