The engine model and serial number is located on the left rear of the engine block, below the cylinder head on a flat spot of the block. The VIN number is located on the driver side door latch pillar on a steel number tag, and on the driver side window pillar (betweent he "A" pillar and windshield) on a metal tag. You should have both the engine and VIN numbers handy as Mercedes has a tendency to make running changes, and everything is based on the serial number.