I found a python script in this forum under the "reverse engineering the gen3..." thread. It only worked on the 1.2.789fmt version of the update_kernel, but it did generate three files as noted in this thread above. I was able to compare these files against the later update_kernel and I found that the boot image and kernal are identical, at least up to 1.5 (mobi) verison. I also hacked the python script to extract the later update_kernal files, but I got incomplete results...
My problem was a corrupted compressed linux kernel that prevented full boting of the unit. I was able to actually download the internal flash memory and compare it to the kernal files and fine the corrupted memory locations. Gettiing it reloaded was a bit more of a pain.
The Samsung ARM Vivi bootloader tool is not very easy. Some hints: THe <x,y,z> choice in the file download menu is for xmodem, ymodem or zmodem, and only xmodem works...
The load memory command has a table for where to load to that looks something like:
1 = Flash
2 = NAND
3 = RAM
so you would assume that the argument would be 1, 2, or 3, but it is actually the word FLASH, RAM etc. This is the same for the BOOT command.
So, I reloaded the kernal to RAM, then booted from RAM. I'm not really sure what else there is...