This one is a bit easier.
De-compile framework-res.apk. Go to \res\xml\ and edit the eri.xml. Change any line containing your carriers name (Verizon Wireless, Sprint, etc.) to what you want displayed.
Now instead of recompiling, all you need to do is push the de-compiled eri.xml to /data/ and set permissions to 666 (rw-rw-rw), and reboot.
Done, enjoy.