How can I embed the actual voicethread and youtube video?
Just to make sure I'm on the correct page. You are talking about:
and you have substituted your flash file for New_page.swf. If this is correct, then no worries. This a flash extension that is invoked with <flash> </flash>. There is also an extension for playing .mp3s that have been uploaded to Wikieducator. See the beginings of an Audio tutorial.