What exactly happens in 5 minutes? Will the dam pre-load button turn into "install" or "play" or something?
From other games that I stayed up all night waiting for at aprox. 12:01 am EST the game will be able to be installed (pre-load is just all the files are on your PC ready to go) The good news is that in Steam the installation is controlled through your settings so it will just unpack. Once done there will be a quick registration note about your license and how to access it and then you are watching the title screens
basically you should be in and playing within minutes of the "not released" lock coming off