I am guessing that you downloaded a .tar.gz file for thunderbird? Not
sure how you tried to install it, but if you can get an rpm (RedHat
Package Manager) file to install from, that is always preferable. With
rpm. you can upgrade a package (rpm -Uvh packagename.rpm), or remove it
(rpm -e packagename), etc. With a .tar.gz file, you have to manually
keep track of where everything gets installed.
That said, the answer is 'yes' to your question about using apt-get. I
don't use apt-get myself, but I do use yum and up2date. In the case of
thunderbird, though, I have not found an rpm (maybe I have just not
looked in the right place). So, don't be surprised if apt-get does not
find the thunderbird rpm.
There is a good howto on building your own thunderbird rpm at:
