Yes you can Overclock that card!! You just need to be safe and take it very slow. Grab ATITool and load it up. then Slowly raise you GPU Core up by 10-15Mhz. Then run the 'Scan for Artifacts' Test for 10 Mins and watch for Artifacts, Errors or extreme high heat. If you pass that little test, Repeat step 1 and raise the Core some more, Another 10Mhz. Keep repeating that process till you hit the Wall and get Errors or Artifacts.
Then set Core back to Default speed and start upping your Memory clock and testing like before. Don't worry about frying your card. You will see Artifacts when You get too high of a Overclock, Then just back your speed down 10-15Mhz and stick with that speed.
There is lots of Overclocking Guides on this site or just google it.
My little guide is a quick and fast way to get it done.
Just take your time and you'll be fine.
And once you have your Max Core and Mem Clocks figured out, You should try to keep your Core near its' max than your Mem clock. If your gaming, Raising your Core clock will net you FPS than raising your Mem. Don't expect too much from Overclocking that card, But maybe 5-8 FPS if your Lucky.
And keep and eye on your temps, If they hit 70-75 C then I wouldn't Overclock any higher than the speed your at to reach that temp.
Good luck, If you have any more questions, Feel free to PM me.