Is there a circuit diagram that shows the final completed product with all the connections.

I'm not aware of one, that also depends on the type of electronics you have. Usually, it's pretty obvious: four wires to each motor, two to the heater, two to the thermistor as well as power supply and USB connection. Make sure electronics and power supply share a common ground, i.e. connect the PSU's housing to the electronics' GND. Gen3 has extra requirements.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

guzzi

There is a G3 wiring diagram.

For the rest, as Traumaflag says- it depends on your electronics you are using.