Upgrade mozilla question

[Stephen Liu <satimis@icare.com.hk>]

Hi all folks,

I expect to upgrade the existing mozilla-1.0 to a later version mozilla-1.5.

# apt-cache search mozilla 1.5
mozilla-locale-fr - Mozilla French Language/Region Package

I suppose only French version being available not English.  I can have 
mozilla-1.5 tarball downloaded from www.mozilla.org and get it installed, but 
having no idea how to remove its existing version, mozilla 1.0.  OR 
installation will automatically replace the existing verion and upgrade it to 
moziila 1.5

Kindly advise.

TIA

B.R.
Stephen Liu