Blarg. Had a nice reply typed up almost ready to submit, and we had a power outage at work. Guess I get to type it up again.
After you gain root access, you need to download the radio update from here
and the JF 1.51 update from here
(assuming you don't have it already).
Copy the radio zip to your SD card and rename it to update.zip. Turn the phone off and boot it into recovery mode (Home + Power). Apply the radio update with Alt+S. Reboot the phone with Home + Back when prompted.
After it boots back up, move/delete/rename the radio zip and copy the JF 1.51 update to the SD card and rename that to update.zip. Reboot the phone into recovery mode again. Press Alt + W to wipe data (can't remember if this is needed or not for going from RC29 to JF 1.51), and then press Alt + S to apply the update. Reboot again when prompted, let it boot up and you should be good to go.
If you decide to go to other builds, the process will be the same.
HTC Droid DNA
UKB DNA 1.2.1
Cubed Kernel 2.4.2
Verizon Galaxy Nexus - Retired while testing DNA
Samsung Vibrant - Shattered screen - Retired
T-Mobile Bronze G1 - Retired