Uh...opening the iBook voids your Applecare unless it doesn't look like you opened it ofcourse. If you're using the external, just plug your external in and pop the restore DVD that came with your 'book in your machine. Power it on and install the software onto your external drive instead of your local HD (should give you an option on which drive to install it on). After that you should be set as long as you use the external to boot off of.