Here's what I'd try:
No promises, but worth a try.
First, verify that your "Appearance" preference pane exists by checking here:
/System/Library/Preference Panes
Yes, I realize you are checking for "Appearance" instead of "General", but I believe that's what it's named in the folder specified.
Also, the "/" is "the top level" of the files on your boot drive as shown in the finder.
Assuming that "it's there" (it should be), just close this window and proceed to the next step:
Go to:
home/Library/Preferences
Locate the file named:
com.apple.preference.general.plist
... and move it to the trash, BUT...
DO NOT EMPTY THE TRASH YET.
Now -- important -- shut down (all the way off)
Wait a few seconds and press the power-on button and reboot.
Get to the finder.
NOW empty the trash.
Try going to System Preferences.
Will the "General" pref pane open now...?
Why you need to reboot:
If the "general.plist" was corrupted, we wanted to move it from the place the OS "looks for it", then create a new, "clean" plist after the reboot. Then you can get rid of the old file.