To be clear... Did the Microsoft Office download window/tab disappear from Safari, did Safari disappear altogether, did the Find Printer window disappear, or...?
If the Safari window is open, minimize the window or drag it to the side, and see if there's a dialog box open. That's something that might gray-out other Safari features. You might have to OK the download, sign in with an administrative password, select a printer, etc.
If the Safari window disappeared altogether, check the Menu Bar at the top of the screen. Does it say "Safari" in the upper left, next to the Apple icon, or something else?
If it says something else, go to the Dock (at the bottom of the screen) find the Safari icon, and click it. Does Safari return?
If it said "Safari" in the upper left, next to the Apple icon, open the "Window" drop-down menu, and try the various options like "Show Previous Tab," "Show Next Tab," "Bring All to Front," etc. These should help you find a hidden tab or window.
If Safari is present but does not respond to any of the above actions (totally frozen), click the Apple icon in the upper left, and select "Force Quit..." from the drop-down menu. Check the list of applications in the "Force Quit Applications" window. When you find Safari, it will either be marked in red as not responding (in which case, select it, and click the "Force Quit" button), or it will be in plain black, which indicates it's up and (presumably) running normally.
If none of that helps, or you'd rather have direct assistance... It's a brand-new Apple product, so you're definitely entitled to free support. Sure, you could go to the Apple Store, if there's one handy (Saturday or Sunday, at an Apple Store, during Holiday Season - good luck getting prompt help without an appointment -
http://www.apple.com/retail/ click the Make a Reservation button in the upper left). You could also go to
http://getsupport.apple.com Depending upon where you are in the world, you may be able to get immediate assistance from AppleCare, or schedule a support callback for when they're open for business.