Yep I think I can help you. Through a process of elimination, counting menu options and downloading the Advanced User Guide from http://downloadcenter.samsung.com/content/UM/200911/20091103173453156/GT-I8000_EUG_Open_Eng_Rev.1.0_091103.pdf
I managed to switch the language
1. Power up the phone (of course)
2. Once the main screen has appeared press the "cube" button.
3. Select the blue and silver cog icon (Settings) at bottom right of screen
4. Select the General Settings Icon, third option down (displayed as a puzzle and cog icon)
5. Scroll down to the last but one option. (Samsung TouchWiz UI is the final option).
6. Three Arabic options are displayed. Select the middle option (English).
7. Select the Arabic option at the bottom left of screen (if the following message doesn't appear then I got it mixed up and it should have been the right).
8. You should get an English message asking if you are sure you want to change the setting (You know you do!).
9. Phone reboots and bingo it should be English.