Recovering data from frozen Galaxy SII

Hi all,

After a full charge from my laptop, my (not rooted) Galaxy SII freezes to the initial logo screen every time I try to switch it on.
I did my researches and the soft reboot (power button+home+volume up) doesn't work, the screen stays black. The only thing I am able to do is to enter in download mode (power+home+volume down).
I am more interested in saving my datas inside (especially sms) than saving this very old device, but as you can imagine I can't access to it via kies.
I've read that Odin could restore the phone, but how does it work and most importantly, will this wipe out my datas?
Thank you in advance!