Steps:
1. Downloaded cm-10.1-20130323-NIGHTLY-i9100.zip and copied to internal SD. Verified MD5 checksum (76d28a8d093cc787336e8edda6bb97cc).
3. Created backup. (I forgot!!!!)
2. Reboot into CWM Recovery.
4. Flashed cm-10.1-20130323-NIGHTLY-i9100.zip
5. wipe cache partition.
6. advanced > Wipe Dalvik Cache.
7. Reboot.
7. Reboot.