Can't relaunch Finder and the menubar is missing
Try quitting Finder using Activity Monitor (in Utilities). It's in Launchpad there too. Scroll down the list of processes till you see Finder, click it and then choose Quit Process from the toolbar. Choose "Force Quit" at the dialog.

If Finder isn't in the list of applications in Activity Monitor, you can manually start it. It's located at /System/Library/CoreServices/Finder.app. If you can't get to it by browsing (because Finder isn't running!) you can always use Terminal. It's in Utilities too. Just type

open /System/Library/CoreServices/Finder.app


into the window and hit return.