Well you can change your CID to one in the States that has already received it and get the OTA update, but that'll require S-OFF which isn't an easy task, especially for someone who hasn't rooted or anything before. Here's a guide to achieving S-OFF if need be:
[S-OFF] revone - DEVELOPER EARLY ACCESS PREVIEW EDITION - xda-developers
However, most if not all custom ROMs now are based on 4.2.2 and Sense 5, so you can just flash any of them. Android Revolution HD 12.0 is basically stock ROM (no visual changes or anything) but faster and provides better battery life. You can grab it from this section:
One Android Development - xda-developers
As for unlocking bootloader, installing custom recovery and flashing a custom ROM, you'll need to follow this guide:
[GUIDE] Complete Flashing Guide | Rooting | Going Back To Stock | 05.05.2013 - xda-developers
Follow every word and do not skip or skim through it.