You need to use the 'fuzzy select' tool to remove the unwanted part of the image. This is the tool you need in Gimp.
http://photo-info.co.nz/files/gimp-wand.jpg
http://askubuntu.com/questions/28108...c-wand-in-gimp
Click with the tool on the are you want to remove.
Add to your selection with shift+click. Use alt+click on the parts you want to deselct.
Then press 'delete'.
You need to learn this simple technique, it is the most common thing you will need to do.
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