Get a terminal and go to the directory containing the .tar.bz2 file.
then extract the archive to /usr/local/lib
then setup the link (don't know why thunderbird works like this...)
sudo tar -xf thunderbird-10.0.tar.bz2 -C /usr/local/lib/
Then so long as your path contains /usr/local/bin before /usr/bin you should be good to go. Try typing just "thunderbird" on the line and hitting enter. I got some warnings running it, but nothing I'm overly worried about. And it picked up all my accounts fine and even went to check for new versions of my addons.
sudo ln -s /usr/local/lib/thunderbird/thunderbird /usr/local/bin/thunderbird
Also, happy 1000 to me.