Well, Anna, congrats! You will grow to love it. As for the mouse, I don't actually like the magic mouse and have bought a third-party mouse I prefer. As for your workspace in CS5, I assume it's like CS4, so take the advice with that caveat. You can set up whatever workspace you like to use (I like the transparent one, so I can quickly switch to the Finder or whatever just by clicking with the mouse) and save the workspace as a default. So set up whatever panels you want showing, the toolbar, and the settings (like Full Screen with Menu Bar--from the View Menu) then save your workspace (Window menu--Workspace--Save) and use your name or something like that. There are some default workspaces available that you can check out (also under the Window menu) to see what works for you.
But, the thing you and Liz are wanting--a gray background--is what you get from setting up the Full Screen with Menu Bar from the View Menu.