Can i do this from the GUI
AFAIK not. Rewriting partition tables is a bit lowlevel, especially when a non-standard layout is used.
However, you could try to just remove everything from /media/sdb1, and then extract sda1-2064.tgz to it. This will only overwrite the firmware rootfs, leaving the directory structure (and the bootloader+kernel) intact. Unfortunately you'll have to be root (Administrator) to do so. Maybe it's possible to use the GUI to do root-things in the filesystem, but in that case I don't know how to. (Why spoiling time in searching for options which will be different in each GUI, when you have a powerful commandline?
First move sda1-2064.tgz to /media/sdb2. Then open a terminal, and type
sudo rm -rf * # this erases all from the current directory (/media/sdb1)
sudo tar -xzf /media/sdb2/sda1-2064.tgz # this extracts everything from sda1-2064.tgz
Now 'safely eject' the disk, and test it in your NAS.
What is xfs repair and how do I execute it within Knoppix (GUI) and would THAT solve my problem?
Probably not. Xfs-repair is a (commandline) tool to repair damaged xfs filesystems. If Knoppix didn't complain when copying the userdata, it seems the only xfs partition (the userdata partition) is alive and kicking.
Hell.... I could not even find my way back from the shell (text and blk scrn) without re-starting the frikin' computer.
Try F11 or Alt-F7, depending on how you came there. (It won't hurt to try both).