Depends if you are trying to break the window from the inside or the outside. It's very difficult from the outside, and much easier from the inside (I cracked my windscreen and needed a replacement, because I was carrying a long piece of wood and it moved a little and contacted the windscreen).
1) Are you me? I've done exactly this because I knew that my car fit a 10' board. Turns out when you're buying rough lumber 10' sometimes means 10' 2".
2) The windshield is laminated glass instead of tempered. It'll crack much more easily, but it'll (more or less) stay in one piece in the frame instead of shattering out into a million tiny bits.
