Whats your monitor resolution?
You can OC the integrated graphics (mine are OCed to 1450) but it won't improve things THAT much. It was like a 30% increase from stock if I recall. I used the ASUS utility which did it for me and all I did was push the "Extreme" button. I play SWTOR on mostly maxxed out settings, but on a 768 resolution monitor. SWTOR is a far cry from Black Ops and I can see the pixels on my monitor which is /fail. I had the same idea as you initially and now I'm monitor/GPU shopping, even for SWTOR.
I googled your board real quick and it didn't seem to have an "ez button" so you will have to do a lot of reading and research before you start overclocking manually. Basically you keep increasing the multiplier and checking temps, then increase the voltage if things become unstable. You put the CPU at risk when you give it too much voltage and most will agree that the number you don't want to exceed is somewhere between 1.38 and 1.4v. But like I said, you should spend a minimum of several hours studying the guides before you attempt this.
In my BIOS the HD3000 has separate settings and I couldn't find much to read about how to OC the graphics.....just the CPU, and I'm pretty sure they are two separate efforts.
I'm sorry, but I'm guessing you will spend a lot of time reading, and OCing only to find that you still can't really play Black Ops to your satisfaction. Having said that, you will probably still have fun learning something new and having an overclocked CPU
, so go for it.....but in the meantime plan on dropping $150 on a GPU.