Hello:
Before you do anything you need to backup your current profile
/home/username/.mozilla
make a backup directory and copy /home/username/.mozilla to it.
Then in your home directory [for simplicity]
mkdir newffox
then place the tarball in that directory [newffox] and with a right click select extract here.
Close down any running firefox applications and then browse to /home/username/newffox/firefox
and double click on the file named firefox and select run
Good luck
Seve