Yeah - get osx - the missing manual. David Pogue always makes things very clear - and usually in a very entertaining way.
One thing you'll have to get used to; usually setting up macs takes far fewer steps than Windows. BUT, out of the box Macs DO usually need further setting up. You'll also have to get used to the file structure. It's very basic and easy to understand but, in OSX (as opposed to mac classic) different things go differenct places - depending on who the "users" are. Fonts are one thing that can drive you nuts. They may be installed in the main fonts folder, in each user's fonts folder, or in a fonts folder connected to an application's folder. Then they might be allowed for one user, but not another, etc. If you put all fonts in the main fonts folder, life will be easier.
Also, make sure that, if your users share and collaborate on docs, that the font families match. Macs come with most of the common Windows fonts like Arial, Times New Roman, Verdana, and MS Office usually installs some more common Windows fonts but, if your Windows users use any special fonts, you'll have to get the Mac version (unless they're Opentype - which is universal)
If you're planning to hook the macs into a Windows network, go to Apple's site and check out info about connecting to a Windows server.