Is there any means to completely uninstall a mod for Oblivion automatically, by which I mean deleting the ESP file and all model/texture/sound whatever files associated with that mod?

Or do I have to go in there and manually delete them myself?

If you used OBMM or BAIN to install it, then all you need to do is to uninstall it via those tools and they will remove everything for you. If you installed the mod manually, then you must remove it manually.

Yes, OBMM or BAIN is best, but if that's to late, you can use http://www.tesnexus.com/downloads/file.php?id=7557.

as said above really, i use OBMM works well and easy to manage.

You might also consider http://www.tesnexus.com/downloads/file.php?id=8489, which can uninstall mods among its many features.

If you installed manually, then reinstalling the Mod with OBMM or BAIN and overwriting the files, then removing the mod would get it uninstall..no need to manually delete..