I would very much like to re-add the components that are missing from the on-board power supply, but am not quite sure what is required. I know I need a barrel connector (or a direct solder connection) but what else?
On a side note, is the VIN pin on the gertduino connected in the same way as the UNO, or is this the pin that's referred to as Vext in the manual, and thus disconnected?