Youre buying a laptop. The display is connected. If you purchased a G4 tower, you would have to purchase a monitor at the same time to get both covered under AppleCare.
If you crack it you buy it. If it goes bad, they pay for it. There shouldn't be a reason for the screen to crack. The duo and the early PowerBooks did have this problem, noted by air travelers. The cause was supposedly air pressure changes. AppleCare does not cover accidental damage or theft, nor do most other computer manufactures. Your credit card might, but usually only on new purchases.
Go to Apple for AppleCare. The eBay is likely legit, but why risk it. You can register online of AppleCare, tax free (its a service), or get the box and get the software on CD.
If your really worried about damaged, look at renters insurance, or go to CompUSA or another company that offers replacement plans for stupidity and bad luck.
Hey, call Apple. I thought you had 90 days to make the decision about AppleCare, not 1 year.
I need a new iBook. Mine is really showing its age, but it still works and looks cool.
Cheers.