Is it neccersary for me to read Countdown in order to better understand Final Crisis?
 
Also, I understand that the entirety of Countdown was unpopular, but would I get anything out of reading the related events like Countdown: Arena and Salvation Run?

You don't really have to read Countdown to get Final Crisis... but suffering through it does help make Final Crisis a little more understandable.

Allegedly, Countdown contradicts Final Crisis quite a few times in its continuity, and I can't recall ever reading any praise for Countdown whatsoever (only complaints) so I wouldn't read it if I were you.  (By the way, I haven't read it either.)

Well thats that sorted, I did find Final Crisis quite underwhelming considering the hype. . .