Heya Jim :)
I had always understood them to be FRU. Check out figures 4-6 in the data sheet.
We recently had to do this on a Nexus 6K and it rebooted automatically when we swapped the first PSU - apparently it didn't like having one of each flavor. No clue if the 4500X is the same way but you might want to be prepared for that.
RMA the switch to be safe, not sure but, surely you can get a new part (fan or power supply) sent to you - any support contracts should have fairly quick turn around, don't mess around with airflow for devices like these, it is not advised at all... and also will not be supported configuration.
Why wouldn't it be supported to order the Power supplies and Fans to reverse the airflow. The use case for this is moving the switch to a new location that requires reversed airflow. Why would cisco build it with replaceable color coded fans and power supplies if it were not supported to replace them with their opposite airflow components.
It is not supported to do this live, and if it is attempted the switch will reload, but I have no idea why it would be unsupported to power down the switch and install the replacement fans and power supplies. If a Cisco resource would like to give us a definitive on whether it is supported or not that would be great.
See note below from installation guide.
Note The chassis determines which airflow direction is correct by polling all of the fan assemblies and the power supplies. The airflow direction for all of the devices must be the same. If the airflow direction of the replacement power supply or the redundant power supply does not match the fan assemblies airflow direction, the system software shuts down the power supply and generates a power supply mismatch error message on the console.