Debian Firefox is now just a transition package which loads Iceweasel, in
stable, testing, and unstable .
mozilla-firefox (1.0.4-2sarge15 at todays's date) is available in oldstable - don't know whether this would have the extensions that you want.

You'll have to forget about using Klik .

Start with a clean purge of iceweasel (and firefox if the transistion package is installed) :
dpkg --purge iceweasel firefox

It's probably easiest to download mozilla-firefox manually and install using dpkg - you might have to fiddle with dependencies as well (apt-get install would probably insist on installing iceweasel unless you go in for pinning complications -see Debian site for instructions if you want to try that).

A better prospect is probably to search the web for a recent Firefox .rpm package, alien that to .deb format and install with dpkg (again, you might have to work through extra dependencies manually. Invoke firefox from a console so that you see any messages about missing .so files)
apt-get install alien
alien <whatever>.rpm

Or compile an installation from Firefox source (see Firefox site).

You should put a debian-type installation of firefox or mozilla-firefox on hold so that apt-get upgrade won't replace it with iceweasel again
apt-get install wajig
wajig hold firefox