Hi Joseph,
When you run the Internet Wizard there is an option to test the internet connection which is checked by default. If you leave it checked and the test fails, it will revert back to the previous settings (Ethernet in your case). But if it does pass, the settings will be changed from Ethernet to Cellular.
When you have a cellular modem and a LAN card installed there is also an option to use the cellular as a fallback connection. If you run the Internet Wizard and select Ethernet, after the Ethernet configuration completes, it will ask you if you want to set up a fallback connection. Then you can enter the cellular settings so if the Ethernet connection is lost, it will fallback to the cellular connection.