I have a friend with a Macbook Air who accidentally spilled milk on his keyboard. Most of the keys are not working. He took it to the Apple store and a rep there told him he would have to replace the top case for a price of $750. I'm sure a certified Apple retailer can do this much cheaper, but is it so hard to just replace it by ourselves? It's out of warranty anyhow, so that part is past. Does anyone have any experience with something like this?