No data is lost at all. Your texts, apps, settings etc. are all kept.
HAVE AT LEAST 50% BATTERY LEFT ON YOUR DEVICE
It is the second link which says download software for USB. Download this ICS update.zip and move it to the root of your SD Card using a file manager or the computer.
2. If you are using the computer, plug your phone into the USB port using a USB cable.
3. Pull down the notification bar and select mass storage on.
4. Go to my computer and then navigate to your downloads folder where you have the update.zip
5. Move the update.zip to the root of your SD card on your phone (not in any folders).
6. Now pull down the notification bar again on your phone and deselect USB Mass storage.
7. Unplug your device from the USB Cable.
8. Go to settings>About phone> System Updates> Update through USB Storage
9. The rest is done for you.
10. Be patient as it may take 5+ minutes.
You are now booted into ICS!
Happy Ice Cream Sandwiching.
IF THIS HELPED PLEASE PRESS THE REPUTATION UP BUTTON AT THE BOTTOM RIGHT OF THE POST (the green up arrow). Thanks
Hope that helped
Edited by i am not a hacker, 30 May 2013 - 11:35 AM.