its pretty simple if you're stock. My phone was stock also.
I assume you are on the latest software...ZV9?
Root ZV9. Download ZVB file and change the name to update.zip and put it in the root... /cache folder. Boot into stock recovery and flash the update.zip. Reboot and Voila! You will be on stock un-rooted JB. Feel free to PM me if you need more help. It's very quick and easy. It took me about 10 minutes.