Yes must be locked first. Go here start at 1 go to #5 replace 1.85 with 2.20 so it makes sense lol.
http://xdaforums.com/showthread.php?p=29710888
I just wanted to take a minute and thank eraste , he walked me through restoring my phone to stock and gave me about an hour of his time. People like this are what makes XDA the place to be. Please take the time to thank him or any of the other people who may help you along your cell phone expeditions. This thanks is for you eraste!