From version 2.10 with Webium’s mod-pack there is no need to uninstall before update. Downloaded files are now stored in \webium-download\ folder – this files are not deleted after installation, so you can manually extract the mod to your game in case of error by extracting. + you get popup with error message. Even by changing the installation, or updating, these files will be not downloaded again. But will be deleted when uninstalling the modpack.
From 0.8.10 there was mod-pack installer implemented (CZ/DE/EN/ES/FR/IT/NL/PL/RO) – with options to install selected mods only. With installer you can easy change, repair or remove the mod-pack from Control Panel, or run “webiums modpack” icon on your Desktop.