It's a lot of work just to get to the keyboard to try to clean it if you can.
This model has two different top case versions 661-5396 (side by side serial numbers - '09 model) & 661-5590 (stacked seal numbers - '09 & 10 models)
Follow this guide: MacBook Unibody Model A1342 Upper Case Replacement.
To try to clean it:
Get a gallon of distilled water (don't use tap water!) in a shallow pan, After removing as much of the hardware as possible (speakers) & pop off the keycaps as well. Try dipping the whole top case moving it about in the water to try to get all of the dried coffee & milk dissolved into the water. Change out the water a few times then dip the case into a pan of a high grade of isopropyl alcohol (85% or better). You want to dip it into a second fresh pan to make sure you have fully displaced the water with the alcohol. Now shake out the case of whats left and let it air dry a couple of days near a window to warm it a bit. Hopefully you can recover your keyboard Vs replacing it.