Try updating your drivers and getting patches. That would allow you to run FarCry decently without spending more cash. And since you don't have too much ram and only an okay graphics card, I advise keeping quality and resolution on lower settings.
If you wish to upgrade, then I advise getting another gig of ram and an x850 Pro. They're both pretty cheap but will really raise performance.
With the RAM, find out how many pins you have, what type of RAM it is, and what clock speed your current RAM is. Also find out if you have an empty slot. For the graphics card, find out if you have an AGP or PCIE slot. And I understand that you want to keep it simple, so you should get CPU-Z.
CPU-Z is safe and easy to use. Launch it and click on the memory tab to check the RAM, and go to the mainboard tab to check the graphics card type.
A list of RAM; get CPU-Z and find out which one you need.
This will cost around $100.
PCIE Graphics Card
This will cost $125 after rebate.
AGP Graphics Card
This will cost $100 after rebate.
More powerful PCIE Graphics Card
This is $156 after rebate.
Newegg is trusted and has great prices, so you can be confident when you buy. I also have recently been researching graphics cards and know the good cards fairly well, and those listed above are good deals.