Early warning signs: Logic Board

Hello
I've just put the screen spanninng doctor on my ibook and am conscious of the logic board failure problems.
To be on the safe side, are there any eary warning signs of a logic board getting a bit to much of a bashing?

Also, is logic board failure covered under apple care, i haven't paid up for it yet (still in first year) and would like to know before i fork over the cash. And i am aware that the hack probably voids warranty, but i'd remove it before sending it in for repair.

Cheers