the keyboard of this laptop is driving me insane!!!! i don't know what is happening, i don't touch any single button but in the screen appear the letter "i" or "s" like i was pressing one of those button constantly. I know, or i assume, i can deactivate the use of the integrated keyboard deselecting an option while i compile a kernel. I don't know if i can do that, and if i can what option in the kernel i need to deselect o select.

thanks for any help and greetings from Guatemala!!!

I know this isn't the answer you're looking for but it will do the job.
If your keyboard has stuck keys, simply google for disassembly instructions and just unplug the ribbon cable for the keyboard. You can reassemble it with the bad keyboard unplugged (until you get a replacement from ebay) and just use a usb keyboard.
If you've already installed Gentoo, it should detect that the keyboard no longer exists and if you're doing a fresh install, it will never see it.
Removing the keyboard is generally pretty easy on a laptop, on most you just open the lid fully, pop off the plastic piece behind the keyboard and then remove two screws securing the top of the keyboard, lift the keyboard and unplug the ribbon. Thats usually it.