71C isn't too bad. I've seen some cards pulling 90+C and still running. Optimally you want 50-60C at full load.
To be honest, unless you know what you're doing I wouldn't OC your video card. It's a long and painstaking process (I know from experience). You have to slowly up the GPU clock, test it, then up the shader clock, test it...rinse and repeat until you find the highest setting that is stable.
If you use a nVidia card, nTune is a free program you can download off their site if it didn't already come with the card's driver disc. ATI has ATITool I believe.
There are also some programs out there that will do it for you, but unless they show you step by step what they are increasing...you're flying blind as you have no idea what caused x setting to become unstable, or when y setting causes your screen to black out.