Did the send screws in the starter pack?
You should just unmount the radiator from the front fans, they will be long and go through both. Then screw the front fans back into the front of the case.
Take the fans off the radiator and turn them the other way around and screw them back on and then screw the radiator into the top of the case.
You may need to disconnect and reconnect the fans and rbg though and reroute them.
It is fiddly, but it is something you can do yourself and better than sending off and waiting.
You should just unmount the radiator from the front fans, they will be long and go through both. Then screw the front fans back into the front of the case.
Take the fans off the radiator and turn them the other way around and screw them back on and then screw the radiator into the top of the case.
You may need to disconnect and reconnect the fans and rbg though and reroute them.
It is fiddly, but it is something you can do yourself and better than sending off and waiting.