Not an AMD employee but you probably should've emailed them prior to doing that. But, if you included the RMA number and all of your info and mailed it to the exact department/address that was on the FedEx label, all should be ok. The outside of the package should've also had the RMA number written on it but not sure if that will be a deal breaker. At worst, it will get sent back to you. I would still email or call support and tell them. You'll wait forever in the forum.
"It worked before you broke it!"