P1456 - Fuel evap system leak
Try replacing the gas cap, after that it could be any number of things from a valve to a solenoid to a cracked hose. Search 1456.
P0401 - EGR insufficient flow detected
Try cleaning out your EGR port. There is a DIY.
P0420 - Catalyst system efficiency below threshold
Could be an o2 sensor or your cat needs replaced. Search 0420.