The oil sending unit on a 2000 Chevy 1500 V8 is located on the driver's side (left side) of the engine block, near the oil filter. It's a small, usually cylindrical, sensor. However, the exact position can vary slightly depending on the specific engine (e.g., 4.8L, 5.3L, 5.7L, 6.0L) and even minor variations within those engine types.
To be certain, you'll need to consult a repair manual specific to your truck's year, make, model, and engine size. A Haynes or Chilton manual, or an online service manual, will show a diagram with the location clearly marked.
