Macbook Pro 15" replacement Keyboard / Keys
Here is an English-language keyboard cover for the European keyboard that you already have. It costs US $30. This would provide a good solution to your problem with no need to install any parts. It is designed to remain in place all the time, while you type, and you can leave it on when you close the MacBook. In addition, the cover provides protection from spills and wear-and-tear.

Make sure you are ordering the exact correct part for your exact model of MacBook.

http://www.kbcovers.com/servlet/Detail?no=487