Gaining speed on the CPU and GPU can effectively gain FPS during many games. Each game will react differently but I will say BF3 did see a bit of an improvement for me from 3.4Ghz to 4.4Ghz on my 2600k.
Now, if you're wanting to overclock you need to read the overclocking guides here in the forum. They are the best information on the web if you ask me when it comes to overclocking the Ivy Bridge processor you have there.
Depending on the motherboard/BIOS you will have many different options for overclocking the processor. But it's best to know what these settings do before even touching it. So I'd advise looking in the BIOS and writing down all the terms you have so you can later research them with Google/Bing. This will give you a heads up of what you have available to you. Every model of motherboard is different; so it's best to do that.
As for your GPU, I'm not absolutely sure as I've never ran the 7850's. I will say this though, with that Ivy Bridge, if it was mine I wouldn't let it get over 70C with IntelBurnTest. But when it's running stock with stock cooling and voltage I have seen the 3570k break 80C while running IntelBurnTest.
So you need good cooling and knowledge. If you're running a stock cooler; I'd be looking into putting some money into a new cooler. If you're going to spend under $75 for air cooling, Hyper 212. If you're spending more than that; look into the Noctua D14 and similar coolers. I have a Hyper 212 and put two different 120mm's on it and couldn't be happier, especially when it cost me less then $50 all together and performs very close to the $80 Notcua D14.