Arduino Project Using PID

I'm building a steam boiler and engine with a generator attached, I know how to do wiring and setup Arduino i just don't know how to code. Basically, the boiler will have a fan attached to blow air into the fire to control the temperature I will also have a hopper for woodchips with a screw and a motor attached to feed the woodchips into the fire. I need to monitor the voltage of the dc generator which will be attached to batteries to maintain a consistent voltage when running and to adjust the fan speed and screw speed to supply enough heat to keep the generator spinning and enough voltage when the load increases. This will require a PID program to have a voltage setpoint to change the speed of the motors to keep up with the load demand. I want the PID to control the fan to heat up the fire then the motor for the screw to feed the woodchips in will be calibrated relative to the fan speed to make sure there's always enough wood chips. Also if the voltage goes too high I would like a relay to disconnect the generator from the battery until the battery voltage goes down.