[ChipnDale]

1. From what you are saying probably not
2. I'm guessing spoils of war, as in the damage to the screen
3. At the moment just make sure you don't sit on it/drop it ect again, if you have a sony store or electronic store nearby take it there they might be able to fix it.
4. If it's still working you may be able to use it for as long as anybody else or it might become unreadable...it's hard to say.
5. It might come back it might not, there is no way of knowing 100%

If you see damage but it doesn't bother you then keep using it but be super careful from now on (I saw a Cybook on here with a damaged screen but the damage wasn't too bad so it is possible) the alternative is to have someone take it to the sony store (you said it's under warranty so from where ever you bought it from) and have them service it.

Good Luck!