I too had a spill on my laptop causing a few letters to not work or randomly press themselves. I purchased an external keyboard with a built in trackpad.
I was able to disable my trackpad and most of the keyboard keys by doing the following:
1. Go into System Preferences
2. Select Universal Access
3. Click Mouse & Trackpad
4. Turn Mouse keys on
5. I enable "Press option key 5 times to turn Mouse Keys on or off"
6. Click ignore trackpad when mouse keys is on
Doing the above turned off most of the letter keys but still allowed the music control keys at the top of my keyboard to still work.