You might be able to do a little basic troubleshooting if you have access to a digital multimeter. The USB +5vdc is isolated from the board's 5vdc bus by a diode D1. See if after you plug in the USB if you have +5vdc on the anode side of the diode but not on the cathode side which would indicate an open diode.
As far as using the ISP method of programming the arduino board that is pretty simple using a hardware programmer or another arduino board running the arduinoISP sketch and then using the IDE's file menu option of upload sketch using programmer option.
Hm ok I got an Open Diode....
What happens when I remove it?
Can I still use the Nano?