Now you can see How to install GNOME on Ubuntu 9.10-Shell Karmic Koala.
First you have to install all the dependencies needed to successfully build and run gnome-shell.
$ sudo apt-get build-dep gnome-shell
After installing all the packages necessary steps for installing veritable gnome-shell
$ sudo apt-get install gnome-shell
Once installed, you can start GNOME-Shell by typing the following command in a terminal:
$ gnome-shell --replace
GNOME-Shell is still under development and therefore very unstable.
Try it in your Test machine or in a Virtual machine.