The programming of 1 motor in a forward direction(right side) to match the programming of another motor in the reverse direction(left side) is impossible to do with the FIRST supplied code. Autonomous maybe, but in telematic mode, that would mean one joystick forward and 1 in reverse just to drive straight. Your robot must be spinning in circles literally.
As far as the victors, they don't care what is attached to the M+,M- terminals. The V+,V- terminals are the ones to be concerned about. Yes, attach the wires reversed there and you will have learned a very expensive lesson and see some magic smoke.
Good luck this season. And as the losing NFL team fans always say: There is always next year. TIP: Find a another close by team to come in and mentor whats left. Maybe the instructor will come around with more experienced input.