If the video data cable has been disconnected before, the adhesive on the might not hold. Be extra cautious in disconnecting this. An illuminated magnifier would be a good help on this step as it is very delicate. This was where I feared I would fail. Was very relieved in getting through this step...
Not necessary, but a good idea, so as to avoid any spurious charges going through the boards...
The screws on the Late 2009 are identical. The blue lock compound might make tightening some require a little more effort.
Another excellent guide. Can be tedious. Good, bright lighting a must, and patience.