Chosen Solution

So I unfortunately spilled beer on my 2012 Macbook Pro about a month ago. I just took it apart and saw the tell-tell signs of corrosion - a green “crusty” area in a small part of the logic board.

  1. Should I even bother bringing this in to an apple technician? They are presumably just going to tell me that its water damaged which I already know. I can’t afford paying them ~$200 dollars to clean it for me so would rather just do it myself.
  2. I’m thinking of trying to clean out the board using this guide. Cleaning coffee/splenda corrosion from inside of MacBook Pro in combination with: MacBook Pro 15" Unibody Mid 2012 Logic Board Replacement Basically my question is, to anyone who has successfully removed / cleaned a logic board is: Where am I most likely to go wrong? Is there anything not mentioned in the ifixit guide which I should be aware of. Have little experience in repairing electronic components and am, understandably, a bit scared of doing this. Any tips would be hugely appreciated. Update
To anyone reading this whose interested in a followup, I successfully did this yesterday. I removed the board and cleaned it with with isopropyl alcohol and a soft toothbrush and got rid of all visible corrosion.  Thanks again to those who replied. The hardest things in the job were:
a) re-inserting the logic board into the case
b) re-inserting the keyboard cable into its socket.
These videos are extremely useful:
http://www.youtube.com/watch?v=OHriXZznK...
http://www.youtube.com/watch?v=aQZ_rG9Vp...
This ifixit guide is good but it can be a little vague at times when describing how to remove the cables from the boards so definitely watch the videos.
A magnifying glass is extremely useful for ensuring all signs of corrosion are gone.
This is definitely  tricky - some of the cables are not easy to pull out / reattach and i was worried at times that I was going to damage them. But if you're patient and logical about it, its satisfying work and its nice not to have to pay someone a few hundred dollars for something you can do yourself.

 Before doing anything yourself, I would take it to the Apple store, give them a sob story, and if they don't help you, offer to buy Applecare if they'll swap the board out.  I know many people who have done that successfully, especially for newer machines.  It's worth a shot.
As far as cleaning the board, though, the instructions in that link look good to me.  You basically just need to remove all signs of corrosion.  Personally I use compressed air to blow away all residue, etc., after scrubbing with a toothbrush...there's less chance of doing damage that way than trying to use a vacuum and/or cloth.  Also, I would disregard the part about taking apart the fan unless there is a specific issue, because you're more likely to cause a problem with it than have any benefit from preventative maintenance (although blowing it out with air never hurts).
I use 91% alcohol and have never had a problem.  Sometimes it takes several rounds of cleaning before you get it all...a board has lots of nooks and crannies, so it's difficult to find all the problem areas at once.  A flashlight definitely helps.  And definitely take the board all the way out, because often there's more corrosion on the other side.  Personally, I wouldn't take off the heatsync unless you specifically see corrosion in the area.
Beyond that, if you get as much alcohol on the board as I do, you'll definitely want to allow adequate time to dry before powering on.  With 91% alcohol you're probably safe after a few hours, or overnight if you want to be 100% certain.

 STUDY THE GUIDE before beginning. Purchase all the recommended tools. Study the guide before you start. Take pictures of your own as you proceed. Study the guide before beginning. Separate an label all the screws. Study the guide before beginning. Use soft bristle brushes (artist brushes, not house painter brushes). Completely dry the board after cleaning before applying power and did I mention you should study the guide before beginning?
Seriously pulling, brushing, scrubbing a component/connector off the board is the most common error, that and trying to put too long or short a screw in the wrong hole when reassembling.
If this Answer is helpful please remember to return and mark it Accepted.

 Be very careful removing + reinserting all cables. Especially display, bluetooth and camera. toothbrush + rubbing alcohol is the best process. First remove the fan and see if the water indicators have been turned orange.. I think that's where they are on this model. If they haven't take it to the Apple Store and don't mention water damage. They most likely will be though...

 Using ice cube trays is a good way to organize screws. Use 1 cube per step. If you have enough, dedicate 1 spot per step/size of screw.
Even better, but a little more money, are the clear multi cell parts boxes. That way you can close the box to secure all the parts in order (even add notes) in case the project has to be interrupted.
Also print out a hard copy of the disassembly guild and MAKE NOTES is you proceed from step to step.
When in doubt, PAUSE!
Take pictures along the way. Re-routing cables is a lot easier if you can see how it looked before began the carnage of disassembly.
ALSO! When frustrated, TAKE A BREAK rather than causing one.

 I just finished following the directions suggested by everyone on this post.
I ended up using 99% alcohol to wash the logic board, and used a soft tooth brush.
It helped with some issues from the spill, so that is good! Unfortunately my wifi still doesn't work - so I'll try dealing with that next.
Anyway - thank you to everyone who posted on here. It was immeasurably helpful - and the whole process oh-so satisfying!