The only firmware you can install is one with the same name (as in Support-Software Menu).

November 2009 is quite a late version. A later one has just been released for European models.

I don't recall any significant user benefits from previous upgrades, and believe they have been for maintenance bug-fixes. Samsung have not made change logs public for most models. The latest upgrade can't be reversed, so I would say don't upgrade unless you're experiencing a problem.

Windows 7 has built-in media sharing. You just need to turn it on and it should appear as a source. Otherwise, the TV should come with Samsung's own server software.