I was running both RCs but only in the last few weeks finally replaced the one remaining 64bit RC with the 32bit retail. There is no direct upgrade from RC to retail plus settings for the 32bit to the 64bit? aawwww....
Once you got retail forget everything but any files you want to keep before a good drve wipe or wipe of the OS primary in case you have second partition for backup. 7 goes on so fast you will want to start off fresh with the retail to see the idea results.
Once you have the retail 64bit up and running depending on which edition you can also see a backup image created. Mainly these options are seen with the Pro or Ultimate editions there. Macrium has a great free for home use version of Reflect available however. http://www.macrium.com/ReflectFree.asp
Previously only having 4 drives two for storage, two for OSs the 64bit retail went on on while the RC was still in use. With a new larger drive added in that saw the second 64bit go on fresh. Nothing like a clean install of 7 once you get things on fresh!