Hi,
you are using incorrect version of pharo.to follow the Pharo by Example book you need to download the right version:
otherwise, you will be hit by the large amount of changes.the recommended way to follow the book is to use the version you have there (which is a bit older) and when you finish, you can jump to the newest version (it will be pharo 3 in a couple of weeks).
cheers,Esteban