Here is a key question: How did you get the developer beta? Are you a registered iOS developer, or did you buy the beta profile from someone selling it on the Internet? If you personally are not a registered developer you have shot yourself in the foot; you will have to restore the phone from DFU mode and set it up as a new phone.
If you are a registered developer and got the beta profile through your developer account the GA release should install smoothly over the beta that you have. Mine certainly did on all of my devices. Actually, it should update to whatever the next beta release is. You can also get help in the appleseed forum as well as the developer forum.