Typed a terminal command to Show Recent on Dock. Must have made a mistake because now everything's screwed up. How do I fix the command?
You just messed up parts of the Dock configuration. Enter the following in Terminal:
Second option (Dock configuration totally broken):
Throw away Library/Preferences/com.apple.Dock.plist in your home directory.
After each of these, enter
in Terminal to restart the Dock (it will maybe take a few seconds to start up again)