Removed Ethernet Interface to solve App Store problem, can't add it back

I was having an issue with the App Store where I couldn't install apps and updates from the App Store, so I followed some instructions from tonymacx86's forums. It suggested removing all network interfaces in System Preferences, then deleting the NetworkInterfaces.plist file from /Library/Preferences/SystemConfiguration. I, not being a completely stupid person, moved the file to a different folder instead of deleting it.

After I restarted, I tried to add the Ethernet interface back, but it wouldn't show up. I tried modifying the plist with some stuff from the old plist, but that slowed my system down to a crawl and didn't fix the issue. So I removed that part again and now my system is running fine. What can I do to get my Ethernet connection back? Can I add the original plist file back again? Or will that bring back the App Store issue?

Built-In Ethernet Adapter Not Showing Up