Your mail settings and your personal account information is in the ~/.thunderbird file. As long as you don't move that you will be okay.
Go to the synaptic package manager or use the ubuntu software center and remove the current thunderbird package. Then add the current mozilla ppa to the sources list
sudo add-apt-repository ppa:mozillateam/thunderbird-stable
sudo apt-get update
you then should be able to open synaptic and choose thunderbird 10.0.2 and install it.
If you have issues there you can always download from Mozilla Team Here just select your language and install the .deb file.
Caution! If you update, - your old thunderbird will be upgraded.
you will also need to "pin" the app or freeze it from further updates by
echo <package> hold | dpkg --set-selections