First, it's either broke or it isn't. Highly unlikely that water damage will get worse 2 years later than it is 2 seconds after you do it. Unless you live in a super humid place like Florida. That being said, I think you can inspect it yourself.
Where did it spill? What Model year? Under the case, on the keyboard? I have had a MacBook that twice sat in water, for HOURS, but it was only touching the bottom case, and the bottom was well machined and nothing got in.
I had a cat puke on girlfriends keyboard, instant fry.
Spilled half cup of beer into 4 year old MacBook, ripped out the battery, poured out beer, disassembled 1/2 of it in 5 minutes.....worked till I retired it 4 years after the incident. Was saved by shielding glued to underside of keyboard.
It all depends on the spill.....do you live close to an Apple Store? Has it been on since the incident?
Either way, plug in your model year over at iFixit and watch the full tare down video a few times, then decide if your comfortable with the disassembly. If you aren't, you live close to apple, try to get them to inspect it.
When the beer incident happened, I did have to replace the internal MagSafe port. It had to be nearly 100% disassembled to repair it. It took about 2 hours for me to disassemble, label and segregate parts. 2 minutes to replace the port. 45 to reassemble MacBook. Part was 10 bucks. Apple wouldn't replace just that part, repair would has started at 500 and gone from there.
Finally, the few times I have been to the Genius Bar they were really cool about stuff. I once cracked my screen, admitted it was my fault, and the dude said "hmmmm, looks like a manufacturing defect to me" boooom, brand new phone. Be nice and honest and they seem to be cool usually, but seeing as how they probably won't do that type of inspection on site, it will probably cost you.
Hell, send it to me, I'll fix it.
Sorry for the incoherent response, I'm sleepy...
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I would seek out an independent Mac specialist ASAP, as they may be able to clean the internals in an ultrasonic bath. longer you leave it the less chance of revival IMHO. Cost of having the MBP cleaned is insignificant given the overall picture.
Apple only deals with such matters within it's own framework, therefore modular repairs are effected which in general will be more expensive. You could ask Apple to send it to one of it's major service centres for a one off lower price, equally much depends on the person your dealing with.
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Better to have it done professionally using an ultrasonic cleaner, as this will remove all remnants of the coffee, even if under components.
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Should have quoted your post in my response. Modular is a good way to put it. Apple will say, "hmmmm this zif connector MAY have got liquid on it we need to replace the whole logic(mother)board!" Or, "there is a little dirt on this USB port, new bottom case!"
Like I said above, I only needed a new MagSafe (power) connector from the beer incident. Apple probably would have wanted me to replace all the ports on that side as well, the optical drive as it was sticky on the outside, and replace the entire keyboard as it was also sticky. I only needed one part though, and that's what a reputable small repair shop will give you.