The official OTA update to Android 4.2 for the Sprint Galaxy Nexus has just hit Google's servers, and you can grab the build (GA02) right now. Here's a direct download link, originally found on XDA. Sextape at SXTP Developers posted yesterday indicating that a leaked version of this build would end up as the final OTA release. Here's the detailed build info:
File size: 102,838,616 bytes
So, now you're wondering how you go about flashing this build, right? Well, you can do it now, but it's not a one-step affair. I've placed instructions below, but proceed at your own risk - the OTA update will probably be going out through Sprint fairly soon, too.