Verizon droid 3 on ATT?

[AC Question]

So I want to bring my beloved Verizon droid 3 back to life on an att go plan mainly for texting. From what I understand I need to load the stock rom, root, band unlock (so it will work on gsm networks, and sim unlock so I can use another carrier's sim card. So far I have loaded the stock rom and rooted the phone. Before proceeding any further I checked settings>wireless & networks>Mobile Networks>network Mode, and I now have the options for Global, CDMA, and GSM/UTMS. Does this mean that rooting the phone did the trick or do I still need to band unlock the phone?
Thanks in advance,
-FatDaddySlim