The VarioCam system on the 3.6L is adjustable with slots in the drive system that allow you to reset the timing if needed, the cam does not need to be replaced to do this. If you have access to the 996 Bentley manual, start on page 15-52 which shows how the system goes together and adjusts using tool 9685.
I'm not sure why the mechanic thinks it need a new cam as the entire VarioCam system can be unbolted from the cam itself.....