A coffee disaster and 60 days later, computer is a zombie

So, a coffee disaster happened 60 days ago, the computer needed 0.3 seconds to turn off and say goodbye for ever.

BUT, not for ever, just today it has been turned on and oh-magic it has actually turned on.

Battery is dead, but other than that everything seems ok. BUT not, it is not ok, it is terribly slow.

My question is, how can I know what is causing the problem? I will open it ASAP but there are 2000 km between us right now. I am having access remotely to it. Is there anything I can do to point to what part has been damaged and is causing this very significant decreased velocity?

UPDATE:

So, finally we got the computer back and could open it. I attach the images of what we saw, it did not seem that bad. We used a cleaning spray (also photo attached) to clean the coffee rests, and assembled everything again.

And surprise surprise, speed was back :) Battery was dead but the computer was completely recovered in terms of usability. Pretty surprising giving the fact that the Apple technical service wanted to just replace everything (asking for more money than a new air).

After that, we have ordered a battery from here (this is the only place in the world that you can buy spare parts of macs? If so, you HAVE to open a "shop" in Europe!), and once assembled everything has returned back to normality.

Not necessary to say that we are very happy :)

Thanks all of you for your comments!