if you are seeing that, it means you are pressing the wrong button, when you go to apply sdcard:update.zip you need to press the home button, if you are pressing the menu button you will get the exclamation thing...when you get to red recovery, only use, back button=select and search button=back....dont ask why lol....
to get your computer to recognize your phone, put the phone in debugging mode, plug it in, while its plugged in restart the phone. when it turns back on try to mount it, if it doesnt mount , unplug then plug it in again and try to mount,,if it still doesnt work ,, go here
Samsung select software , try different drivers with the process i just stated above