Nothing is beyond fixing, not if you know what you are doing. I just point in the direction, its easier to go about things once you know what to look for, of course it depends on how much calibration he needs. One of my cameras needed new CDS/Photo-resistors and I just gave it some extra EV range by changing from 1.5 to 6v using 2 cr1616 and compensating on the high end of the EV range with a bigger Variable Resistor on the post-CDS section of the circuit (this controls high light situations and wont mess with low light sensitivity.) After that is just a matter of tunning (move the variable resistors) up and down to let more current or less pass through the circuit as to the meter needle align with the markings.
Can you think of any better ways to totally screw up the calibration of the camera?