The system rebooted, and went to the screen with the android's belly open and the blue spinny thing. Then he was on his back, with the dreaded red triangle. I wasn't surprised that the update wasn't going to work with my modified phone.
This excellent post on xda-developers gave links to the official OTA updates for the different versions of the G-Nex. So I downloaded the mysid IMM76K from ICL53F update.zip, and adb push'd it to /sdcard. Rebooting into recovery, I tried to install the update, but it failed with:
assert failed: apply_patch_check("/system/app/VZWBackupAssistant.apk".....
I knew why it was failing. I had removed some of the VZW garbage apps that cam pre-installed. Luckily, I didn't actually delete them, I had just renamed them to .apk.REMOVED. After putting them back1 the update installed successfully.
Another thing to note - I didn't realize it, but the xda post pointed out this important detail: Verizon updates include a script that runs every boot, whose purpose is to restore the recovery image if it is not the expected stock image. The script is at /system/etc/install-recovery.sh and the recovery image (for flashing) is /system/recovery-from-boot.p. Thus, if you don't wan't to lose (or other custom recovery), you need to rename these files.
1 - I didn't realize it, but ADB is supported in CWM. When I looked in device manager while my phone was connected and in CWM, I saw one device just named "Full". I manually specified the same Samsung drivers (already installed) from before, and bingo, my phone showed up in adb devices.