>>> The Firefox icon has gone from the icons on the left side of my screen
I assume that you're referring to a desktop shortcut. Click on 'Start', then on 'All programs'. Right-click on 'Mozilla Firefox' and then select 'Send To > Desktop (Create Shortcut)'.
How is your printer connected to your computer? Is it by wifi or with a USB lead? (If it's by wifi it might be that it's no longer 'talking' to your router; try turning the router off, waiting for a minute and then turning it on again).
If you try to print, say, a Word document, what happens when you press Ctrl and P together (or go to File > Print). Does your printer's name appear in the box that comes up? If so, what happens when you click on 'OK'. (i.e. what error message, if any, do you see?)