APK is as far as I am aware just the type of file phones play. I personally don't have much to do with APK, so I am by no means an expert on it. I just now that when I press Android Build, APK is what is coming out. So, you should be good to go, so enjoy. =3
Pretty sure for .apk files, since it's just the file that will install an app onto your phone, it will give you an update prompt when you download a new .apk and try to install a new app through it if the app name is the same as the old one.
tl;dr: No, you won't have to uninstall it, lol.
Though uninstalling the .apk file is fine since it's not the app itself.