The title says it all: a cup of coffee spilled over the palmrest of my MacBook Air. My very first (and thus likely the last) cup of coffee if you'll believe it.
About three hours from start to finish. I actually bought a replacement keyboard from another supplier since I didn't need a whole new upper case. Do note that this route is not perfect, just cheaper: the keyboard is riveted into the case and you have to break those rivets (and possibly the keyboard, which in my case was already dead). The toolkit and mat definitely helped.
Be very, VERY careful with the small speaker connectors and pull up at an angle. I broke the plastic around the connector itself on one speaker by accident. Luckily enough plastic was left to just stick the leads back in and it still connects, but that is the one thing I personally would pay more attention to if I had to do this again.