EDIT: Installed RC3 + GAPPS over CM 6.1 RC2 without wipe. After reboot, GAPPS were missing. Reverting to RC2 nandroid and flashing RC3 without GAPPS.
EDIT 2: Flashed without GAPPS but they were still missing when I rebooted. I installed GAPPS separately, it made me re-sign into my google account, and things seem to be running well now.