Keyboard and touchpad with strange behaviour

Hi,

I'm posting here as I've a small problem with a macbook of a friend. The keyboard has a strange behaviour (wrong letters for keys, and of course it's not a language settings problem). I suppose it's a water problem but the touchpad has problems too.

When you move your finger on touchpad top left corner, the touchpad stops working for 2-3 seconds and then works again. I suppose it's a water problem too but how can I check if I have to change both keyboard and touchpad or mother board ? Do you think it could be the motherboard or the keyboard would always take the water first?

I've also read that some people found keyboards on ebay to avoid an all top case replacement. Is it trustable? Do anyone know a good ebay seller?

Thanks in advance !