I think you can plan this up the wazoo and it won't work the way you want it to.
You have to tailor the approach to each user. You can talk about benefits (far fewer viruses, lower overall cost over time, machines that don't go out of date quite so fast, etc.) and they won't care. For the most part those things are justification after the fact; they just want to get their work done, and they need to be assured that they will be able to get their work done.
You may need to dedicate plenty of initial time just holding hands while showing them how to get the initial bumps worked over. They won't want training or reference tools unless they absolutely must (granted you may have some people that will use a Dummies guide or any other quick switcher's books available on Amazon or B&N) in a pinch, but really, the ones that will refer to other things for help will probably already know how to use Google or they'll call you up.
You may even need to arrange for remote access to their systems so you can help in a pinch remotely until they're happy.
The best tool is enthusiasm. Sell the idea to a few people who are already somewhat familiar with the Mac and have them evangelize it internally. Let others see how they get their work done with it. Most employees in our organization prefer getting immediate help from a neighbor, if possible, rather than stopping and contacting us, where there's usually a wait involved and they just want to get their tasks completed. Getting a keyboard combo or a "how do I..." from someone at the next desk will make them happier.
You can spend days making mini-movies, providing links, making charts...and you'll still get calls about something you JUST showed them.
In my experience, seeding enthusiasm and positive experiences will go a long long way for gaining acceptance of the new product. Make sure everything they need to do, from special software to favorite websites, works on their Mac. Find out and test that their workflow is uninhibited. Don't do a mass-rollover. A couple people at a time, and address their concerns as soon as possible, because otherwise one bad person in the bunch will quickly spread word about how the evil IT department is making everything ten times harder, and then even a minor glitch is suddenly the end of the world and you'll get the brunt of their complaints about something that should be a minor hiccup.
We haven't converted everyone, but we did make a significant dent in getting Macs into the workplace. I won't get into details here, but many people ended up liking them more, and more people didn't care one way or the other. They just want to watch a movie, or type a letter, or get on YouTube. The platform isn't the key. It's allowing users to get their work done with minimal hassle.
After you get warm fuzzies from positive acceptance, then bring up things like lack of malware and ease of use. These are things that help after the fact. Otherwise, just be there for them, and be prepared to get them into the groove of things. They're going to panic because it doesn't look like it used to or work in quite the same way. Videos, posters and books aren't going to blunt that!
