STBX wife has a 2001 E320 wagon. Just changed the oil & brake pads for her this weekend.....

Sit in the driver's seat. Put your hand on the parking brake release (that handle with the P on it). Now lean forward, and drag your hand along the underside of the dash towards the floor - stay left of the brake pedal.

You'll feel the hood release lever (or the gap in the dash where your fingers wrap around the end of the lever so that you can pull it). Pull it down and back towards you. Bingo - you're in!