No, normaly what happens on a repair is that it just verify's all the files on your computer to their manifest. If it detects that any files are corrupt, it should ONLY download those files, not the entire game unless something is really messed up with the install. It should only take a few minutes to normally do a repair.
But yes, if you open the Launcher and it comes up with the REPAIR button instead of PLAY, always shut down the Launcher first and try it again. They have had problems with the launcher, well, since the game was launched