In the past I've relaunched finder by using Force Quit (Command + Option + esc). The problem I've had is that while this quits Finder, the Finder doesn't reliably restart. Here is a way that I've found that reliably quits AND relaunches Finder. In the Terminal, type:
killall Finder && open /System/Library/CoreServices/Finder.app
Alternatively you could do:
% ps -caux | grep Finder
to find Finder's PID, and then:
kill pid# && open /System/Library/CoreServices/Finder.app
To kill and relaunch the Finder (where pid# is the PID from the previous step).