Hey there,
Actually it's pretty straight forward, and relatively easy to do. Like OC'ing any component you need to test.
In the nvidia control panel, choose to make a custom resolution. Leave everything as it is at default, but change the hertz to 75. You don't want to go over the top (50% is most likely not doable). So start with 75hz.
Test and the apply the new settings.
You then need to test properly for skipped frames, which you can do here:
https://www.testufo.com/
Follow the instructions exactly. Specially the part about the camera you use to take a screen shot, of UFO running whilst in 75hz. If the picture you take has funny breaks in it then it's dropping frames. If there are no skipped frames, then your monitor will take the OC to 75hz. You can try push the hz beyond that, but most 60hz panels won't to much more than that.
With, that said, it 'can' decrease the lifespan of the monitor. So if the monitor was expected to be fine for 5 years, you might get 4 years out of the OC.
I've a 60hz monitor OC to 75hz for the last 3 years. It's Ben Q. Not a single issue with it.