[LarfinGiraffe]

My kobo Touch is stuck at the "powered off" screen.
When I power it on I get a green flashing light for a few minutes, then nothing.
I have tried all the usual suggestions: 24-hr charging, home+power reset, paperclip reset etc etc but nothing rouses the beast. Sometimes I get a blue flashing light instead of the green one but nothing else changes.
Before I trot off down the shops and get a new one, I'm thinking that it might be worth flashing the internal sd card. After all, at this point I have nothing to lose.

I'm a complete novice at this with kobo, although I did do it with my phone a few years ago! Could someone please help me through this?

The Kobo is 15 months old bought Dec 2013, and the box says its model N905-KJP-S. I don't know where to find the serial number or IC or FCC (do I need these things?).
I have figured out how to open it and remove the SD card!
I have access to a linux box (linuxMint) and a Windows box.
Please can someone send me an image and some instructions on what to do next?

Thanks very much