well ive had css since launch back in 2004. i think its great and i still have it installed, its definatly one of those games you will buy and keep on playing. granted i dont play it everyday but every once in a while i feel the urge to play it.
to start off with i would keep to small deathmatch servers until you get used to the game, maps and aiming.
as for trying before you buy, ill see if i have a guest pass or something.
EDIT: sorry i dont have a guest pass for it, but isnt it just like £5 off steam?
oh and your card will handle it fine, granted your cpu is up to the task. (id say at least a low end dualcore for comfortable gaming).