Typically, you would not open the Power Supply at all, but instead send it in for a replacement, at least if it's still within its warranty period. For the CX750M, I believe that's 5 years, at least in the US, though that model number has been around for longer than that, so it's possible yours could be out of warranty if you bought it a while back. Of course, if they can tell that you opened it, they may not honor the warranty.
It's also generally not a great idea to work on power supplies if you are not sure about what you are doing, as they contain capacitors that can retain a potentially lethal charge even after they've been unplugged for some minutes. You should avoid touching random contacts on the underside of the board, as they could potentially short a capacitor. And of course, you should avoid working on the PSU while its plugged in.