I had that configuration and it works just fine.
I'm a great believer in the KISS principle.
Configuration is simple if you start from a factory default condition. Then connect the Airport to AC power and finally to the 7500. Open Airport Utility on your Mac or other computer and accept all of the recommendations. After confirming that it works, insert your desired administrative and WiFi passwords.
Do not expect the Airport to respond instantly to the configuration commands. BE PATIENT!