To be certain, you'll need to consult a repair manual specific to your 1995 GMC Sierra's year, make, model, and transmission type. A Haynes or Chilton manual would be a good resource. You can also try searching online for a diagram specific to your transmission.
Looking underneath your truck, near the transmission, is the best approach for visual confirmation after you've consulted a manual or diagram. The sensor is usually a small, cylindrical unit with a wire harness connected to it.