constant use of killall Finder 12" MacBookPro late 2012, OSX 10.9.5

Something is wrong with the Finder. When I try to open a new window one pops up, but the interior is the color of the background, nothing inside, and it reflects the image of anything that is dragged over it: 





Those windows start out blue like the background, but are grey here because to take a screenshot I had to drag the grey rectangle over the finder window. They close just fine.

To open any working window I have to open Terminal and type killall Finder, but this solves the problem for a short time. (Sometimes the space of only one window opening.) Also, the desktop does not reflect saved files there until I restart the Finder, and I cannot manipulate anything on the desktop when the Finder has crashed.

A very small amount of water was spilled on it (over the battery and speaker) awhile ago, could that have caused this? What could be wrong? I've seen similar issues posted online involving software installation, but can't link any new installations to the problem. How can I resolve this?
Before we begin: Make a backup of your Data e.g. with Time Machine or similar Software (if you not use Time Machine).

Note: All steps are complete in itself. If one of the steps work, you're done. 

Step 1: Boot into Safe Mode


Restart your mac and hold down the Shift-Key during startup.
The startup process is slower and possible you got a flashing screen. This is normal.
Login and open the Disk Utility. Choose your Systemdrive and click on the buttons Verify and repair disk permissions.
Restart the mac and test.


Step 2: Finder Preferences

Sometimes the Finder Preferences may be corrupt so you can delete this files to return to Standard configuration.


Click on the Finder Desktop and press the keys Command + Shift + G
In the small Window copy and insert the following Line ~/Library and press Enter.
Search for the following folders and move the bold-marked files into the Trash.

~/Library/Preferences/com.apple.finder.plist
~/Library/Preferences/com.apple.sidebarlists.plist (if exists!)
~/Library/Saved Application State/com.apple.finder.savedState
~/Library/SyncedPreferences/com.apple.finder.plist


Note:
Maybe some of the files (folders) not exist on your system this is ok. 
Please don't delete the files until test that works.


Restart the mac and test