Yeah, you can do this without hurting your data since Unity isn't even connected to the directory at all until after you run the configuration setup.
It's not an entirely hot idea to construct a bunch of call handlers and the like while in this state, however, since you can't setup recipients/owners and the like without subscribers (i.e. everyone will have to be owned and leave messages for the example administrator) but this is doable if you're careful.
Jeff Lindborg
Unity Product Architect/Answer Monkey
Cisco Systems
lindborg@cisco.com
http://www.AnswerMonkey.net (new page for Unity support tools and scripts)