Hi,welcome to SevenForums and welcome to the superior world of Windows 7.
Here is a tutorial for getting the quick launch toolbar back Quick Launch - Enable or Disable
normal show desktop will also be available within the default quick launch toolbar.
But you can also hover your mouse over the very right of your taskbar, that will enable Aero-peek, and if you click there it will minimize all active windows i.e. show desktop.
What's cool about this function is that if you click it again it restores all the windows that were open before you clicked it to show desktop, so you don't have to manually open each window again.
The tutorials section is very helpfull, don't hesitate to ask, the people here are very friendly.