For future reference, I'm going to keep editing this particular post with URLs I find online that seem vaguely useful. There's a huge amount of not-useful stuff out there.

Here's a nice description of how to backup an Android device (contrasting nandroid vs. Titanium Backup): http://www.androidnz.net/2011/10/at-your-own-risk-how-to-backup-your.html

Pointers to lots of Jellybean ROM images: http://rootzwiki.com/news/_/articles/jel...xus-owners-r951

When you're dumping lots of new files to your SD card, they don't show up via MTP. The solution? An app that forces a re-scan of the /sdcard directory: https://play.google.com/store/apps/detai...LnNkcmVzY2FuIl0

This seems to be the ROM of choice for a "stock" Jellybean experience on a CDMA/LTE Galaxy Nexus. The thread has a lot of discussion on GPS and battery life issues. I'm going to try to follow the advice about clearing the Dalvik cache and such and hope it all works: http://rootzwiki.com/topic/28992-rom-razors-jelly-v26-verizonjelly-bean-41-8-july/

After all that, I ended up with what might as well have been a fresh new phone running Android 4.1. Not too painful. The actual painful part is getting all my apps restored. The Google Play Store apps are all downloading automatically, but restoring their state is where that Titanium Backup will come into play. And then there are the Amazon Store apps, which you have to reinstall one by one. Much more annoying.

Between this morning, when I installed v2.5, and this evening, the dev who made the above ROM released a new version (v2.6) which fixed some bugs. Upgrading wasn't too bad. I followed the instructions (wipe the cache and Dalvik cache) and everything came right back. No need to wipe and reinstall.