Im running this hard drive
HGST Travelstar 7K1000 HTS721010A9E630 (0J22423) 1TB 7200 RPM 32MB Cache SATA 6.0Gb/s 2.5" Internal Notebook Hard Drive - Newegg.com
Using this RAM.
Team Model TSD316G1600C11DC-E Laptop Memory - Newegg.com
but we need to check your model number to make sure it's correct, in About this mac->System report what is the current Type and Speed of the installed RAM. If DDR3 then that RAM will work.
BTW, you'll now see ads for crap like MacKeeper, ignore it. OSX is a .nix so it runs regularly scheduled maintenance jobs on its own. It also defragments on its own.
You don't really need Anti Virus but if you are suspicious get ClamAV,
ClamXav it's free and I use it occasionally when I'm forced to download something from a sketchy source.
Occasionally the system will get sluggish, almost all the time that is Spotlight indexing the drive so it can find stuff instantaneously. You can check foe indexing by clicking the magnifying glass upper right, if indexing it will say so and performance will return to normal in a couple of minutes.
If you get the harddrive/ram let me know, I'll pop it in for you.