This will mount your rootfs, userfs and emmc paritions so you can retrieve whatever data you require...You won't need to touch your phone at all except for switching it off before plugging it in...
Let me know if you need any help with it...
P.S. The above requires a Linux PC so use a LiveCD, Wubi or dedicated Linux installation. Ubuntu is the easiest to use if you have not much prior Linux knowledge...
I was gonna suggest connecting it to N8 via USB OTG to back it up, but then I realized you'd still need to enter lock code.
Architectural Engineer and Graphic Designer.
[Contact me for any designing work.]
Portfolio: AKstudios : : graphics with attitude.
Flickr: AKstudios
Twitter: @flopjoke