hey guys..iam new in this whole stuff..iam a mobile guru..but a computer newbie..

so,i was recommended by ASRock website to register to this forum...since i got a half-completed pc

here are the specs:
*ASRock N73V-S

*4 Gb RAMs

*CPU: Intel core 2 duo 2.4 Ghz

*video card:its Nvidia 7100 i guess

so my questions are:
-could i upgrade my video card to Nvidia 9500 (i might get the 9800)? because this motherboard have built-in video card

-what is the gaming experience using these specs? games like: assassin's creed II/NFS: Shift/COD: modern warfare 2

-i want to over clock my CPU to 3.0 Ghz is it possible?

--I know these specs are very outdated,but i used to own a laptop..and they aren't for gaming,so i got this and willing to buy new parts..upgrades in the future

Thanks :)