OK...I'm going from an FS series, not an S series, so things will be slightly different, but shouldn't be far enough off that you can't keep up.
1 - remove battery [usually has a lock switch to unlock, and then a release lever on the other side]
2 - Remove the 2 screws revealed when the battery is removed [very fat flat ones, philips head, also very short, so don't be surprised when 2 turns does it]
3 - flip the laptop over and open the screen all the way as far as it will go
4 - take a small flathead screw driver, and gently pry up the panel above the keyboard that has the power button and more then likely some status LEDs on it [cap lock, etc]. This is held down by plastic latches/hooks [9 across the front, 5 in the back, one on the right side, and 3-4 elsewhere at random, I think it is]...so you'll feel like you're about to break it, but you're not. [If this makes you uncomfortable, take it to a repair shop, they should be able to replace the keyboard for about $30].
5 - Now, after removing this, there are 4 tiny screws at the top holding the keyboard down...remove them.
6 - Pull the keyboard up from the top, then slide it out at the bottom, and you'll see the connector. Laptop connectors look like strips of tape/plastic. Pull it out to disconnect it [there's no plug...the end has exposed traces that slide into the connector on the mainboard...so just...pull]
7 - now reverse the process with the new one to install it
Like I said...this is instructions for an FS series [FS640/W to be exact] so it may be slightly different, but the principle is the same...remove the battery, release the top panel where the power/LEDs are between the keyboard and monitor, release/disconnect the keyboard.
Hope that helps!