I think your making this more complicated than it is, think of it as just replacing your existing gauges with another one. The hot or trigger wire from the new gauge can be plugged directly into original harness plug that hooked to the back of the OEM gauges panel, you just need to follow the hot or trigger on the OEM guage panel circuit board to each gauge to figure out which one to use for your new gauge.
Ok so I do need to cut the pin connector and just plug it in into my gauge. Problem is I dont know if the wire colors of the connector is the same as my gauge's, on top of that he had an aftermarket gauge installed that I needed to unplug