Although I have no real qualms with either the Samsung keyboard or calendar, you're going to want the Google Calendar and Google Keyboard apps to really complete the stock Android look. Neither of these apps have any real benefits over the ones included in the Galaxy S4, I'm just recommending them to be throrough.
Once those apps have finished downloading, press the Home button on your phone and select Nova Launcher from the prompt that pops up. Your home screen will resemble the stock Android home screen, albeit with a few extra animations for opening and closing apps.
Remember those apps you couldn't uninstall? The paid version of Nova Launcher offers the ability to hide those unwanted apps from appearing in your app drawer, and might be worth investing in if you're sick of seeing that NFL Mobile app on your phone. It's not the same thing as actually removing the apps, but it's out of sight, out of mind, right?
You'll need to setup Google Keyboard and WidgetLocker Lockscreen before you can use them, but the process is dead simple. Just follow the onscreen prompts. Google Calendar will display the calendar for whatever Google account is the default for your phone, so there's no setup required. If you prefer Samsung's keyboard or calendar, just uninstall Google's.
What we can't change
Even though your Galaxy S4 now looks like the one you can buy directly from Google, the changes we've made here are mostly cosmetic and don't extend much beyond the home screen and lock screen. The dialer, notification shade, messages, and many other parts of the operating system will look the same as when you first picked up the phone and they can't be changed without rooting the device—a somewhat complicated and warranty-voiding process.
Another downside of not owning the Google Play edition is that system updates are still handled by your carrier, so your Galaxy S4 might not always run the latest version of Android. This may open you up to security vulnerabilities and means you might miss out on cool new features down the line.
But a big advantage of not having a Google Play Edition Galaxy S4 is that you can always undo your changes and regain access to all of Samsung's extras and goodies. Samsung included a number of noteworthy additions to the Galaxy S4, none of which you get access to if you bought your phone directly from Google. You take the good with the bad when you buy a phone on contract, but at least this way you get to experience the best of both worlds.
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