I'm trying to think of a way to make my PCs taking the Apocryphon oath a little more dramatic than saying "you are led before the door of the Omega Vault and take your oaths of service blah blah."

Finding some actual excerpts of the oath itself would help. Does the copy that comes with the Collector's Edition have any real info or is it simply a line or two?

I'd really like to make the whole event more interactive, since it should be a solemn event where Space Marines add another duty to their already indentured existences.

The Collector's Edition oath on box is the full oath, however I do not know where one might find a transcript though.