The simplest way to upgrade the board is to use sysupgrade. It allows you to update without worrying about nand partitions and TFTP booting:
To use 0.10.4 you need to use this wget url: http://downloads.creatordev.io/pistachio/marduk/openwrt-0.10.4-pistachio-marduk-marduk_ca8210-ubifs.img. Once you have completed the steps, the board will then reboot into the updated image. The terminal welcome message should make it clear that this has worked, but you can also "cat /etc/openwrt_version" to check the update has succeeded. If the guide on docs is not clear enough, let me know and I will add to it!
The NAND image size should not be an issue for you, so no need to make any provision for this.
OpenWrt-1.0.0 was just a placeholder name in that doc, 0.10.4 is the latest image, though a new Creator image should be released this week (we'll post everywhere to let people know when it's done!).
Optional waffle about NAND partitions(!):
You don't need to worry about the firmware0/firmware1 at all using sysupgrade, but if you're curious I'll try to explain what's going on! Ci40 has dual-nand partitions, so the boards NAND is split in half, meaning you can have 2 installations of OpenWrt on the board. This is primarily useful for upgrading, as you can flash the 2nd partition while booted from the first, then reboot into the other partition (this is basically what sysupgrade does) leaving a backup should the update fail. firmware0 (aka mtd4) is the first partition, firmware1 (aka mtd5) is the 2nd.
I have on a couple of occasions actively used both partitions for working on 2 different projects in parallel without mixing them up, but I think that's slightly abnormal! Most people will only have the second image as a backup from their most recent update.
I hope that helps, let us know if you have more questions/curiosities,