Check out the BlackBerry 101 How-To Lecture Series ! This will help you with the basics such as downloading apps, themes, wallpaper, ringtones. It's also a good idea to browse the forums and read as much as possible. Many questions you have are answered there already!
Thanks PK! And this may be a dumb question/actually I feel lazy at the moment but is there a shortcut to see threads or replies that have been posted by ME?