Hey there,
The short answer is yes and yes
You can OC your monitor. Most 60hz standard panels will OC to 75hz. Simply to the the Nvidia control panel , change resolution settings, customize and then custom resolution. Change the refresh rate to 75hz and test. Then save settings and exit. You can then use something like this to check for dropped frames :
UFO Test: Multiple Framerates (testufo.com) Take a shot of your screen with a decent camera to determine if you have dropped frames. Then play some games and see how it feels. If you notice any artefacts or issues, then roll back to normal res straight away. It means your monitor will not work very well with 75hz. You can try lower at 70 or 65, but not much point any lower...