To create an image of the original firmware you just need a serial access, see #5 (serial pin layout), #66 (link to opening the case, plus high res pic of router's inside).
Ground is soldered to the audio jack's ground, Vcc is not soldered, TX and RX go to audio jack's left/right channel (test if no signal, then switch).
I suggest to get serial access on your current router first, before buying a 2nd one.
If it works, you can get a 2nd one, create images of the original firmware and maybe return it to the dealer (so open it carefully).
With serial access you will see what is going on inside the router before Linux is even started.
The output will be similar to the one from #5.
Note the "Hit ENTER to stop autoboot" message in line 46.
You have 3 seconds to stop the autoboot, this will give you access to the U-Boot system, which offers you to load a ramdisk image without flashing or even flash directly any image.
Please read the complete thread to find out U-Boot commands and more details (reading the complete thread is really recommended).
You can also ignore the message and start the original stock kernel.
When loaded hit enter to get a shell, where you can call all available Linux commands.
Add an USB drive/stick via the web interface of the stock firmware.
Then create images from the mtd partitions to the usb drive/stick via dd.
List of commands for U-Boot and Linux, so you can get all information in one go.
For the log you should set Putty's scrollback to 9999 lines or more under "Window" for the COM connection.
Then call "boot" to get to Linux
ls -l /sys/class/net/*/device/driver/module
PM me if some command is missing.
To find out the PCI device check here (section "PCI addressing")
PCI databases are here and here
"cat /proc/bus/pci/devices" for me results in "0138 168c0023 ..." and vendor 168c (or here) is Atheros.
cat /proc/mtd # to get the numbers (X)
dd if=/dev/mtdblockX of=/path/to/usb/mtdX.img
By the way, after re-reading this thread I recognized that DirkNL has a v2.1 (see post #70).
But this seems to be a different EU version (he's from the netherlands) with the old PCI WLAN card (quote from #73: "I couldn't see any difference between your photos and my WRT").
His v2.1EU logs are in post #78.