you're right - rooting and unrooting are similar - it is basically the same procedure as installing an official firmware update.
the backup procedure is just another way to ensure that rooting / mods can be undone.
unrooting restores everything to stock. if you installed enableadb package or apps2sd package, you'll have to install the related uninstallpackage, too.
finally, I'd do a factory reset which wipes data and reader partition.
now your reader should be 100% stock, provided that you didn't alter partition table or touch other partitions than data, reader and system partition...