will uninstalling and reinstalling iTunes on a Windows 8 laptop mean losing my Playlists?

No

your media files will not be effected.

As given above updating or reinstalling iTunes should have no adverse effects on the library and its playlists, but you ought to backup your library anyway.

See Troubleshooting issues with iTunes for Windows updates for additional information if the reinstall doesn't go smoothly.

tt2

You're welcome. 🙂

tt2