You're getting it!
Early GPS units didn't have the indicator lights (I know, I have one...) but it should be pretty easy to tell. (1) Is there a GPS antenna in the box and a gold connector on the back of the gauge for the coax cable? If so, GPS. (2) Are there two separate multi-colored wires like the ones you had out of the water temp gauge, in addition to the power and lighting wires? If so, not GPS and those wires are for the speed sensor in the transmission.