Change is its own essential skill set. Analyze the technology changes, the business process changes, and the responsibility changes, and describe the change in culture.
Talk loudly, smile, and carry a big "parking lot". You can train anything with confidence and ease using the right tools, even when you don't know all the answers. Secret: you never do.
Stand up a lot, bring laughter, and make the class fun. It's all right to take a moment during an activity to recoup your energy. Then, when eyes are on you, pour that energy into your audience.
Adults learn differently. Utilize their existing knowledge; collectively, they always know more than you. Let them learn independently; they need to be able to carry what they learn into their own environment toward their own goals with their own motivations. Give them group activities; adult learners work effectively through interaction with peers and colleagues - their learning has a corporate context. That said, teaching children can really drive home an understanding of learning styles that persist through adulthood. Utilize multiple presentation methods.