There is no separate installer for the “free” and the “advanced” versions of DAZ Studio. The installer for DAZ Studio 3 is exactly the same regardless of whether it is the free or the advanced version. The serial number determines whether it behaves as the free or the advanced version.
Studio 3.x (64-bit) is always the advanced version. There is no free version of DAZ Studio 3.x 64-bit. It is possible to install both the 32-bit version and the 64-bit on the same computer. Each installs into its own folder.
Always let the DS installer uninstall the previous version. If you don't, parts of the previous version may remain and conflict with the new, updated version of DAZ Studio. Keep in mind the installer is not a true 'updater.' It's not modifying the installation of DAZ Studio–it's installing it from the ground up. For this reason, it needs to remove the existing install first.
Keep in mind that the installer only affects the application. It does *not* remove your content already installed, although you will still have the opportunity to change the content configuration, if you choose.