I'm pretty sure there were no releases between 5.0b7 and 5.0 final, so I'm not sure why Firefox was prompting you to update. But in any case, you can download

I'm pretty sure there were no releases between 5.0b7 and 5.0 final, so I'm not sure why Firefox was prompting you to update. But in any case, you can download any release manually from ftp://archive.mozilla.org/pub/mozilla.org/firefox/releases/