So I'm back with some updates... finally got my system back up (and this is my first build as well, so we're in the same boat), audio, Wifi, and USB 2, Nvidia Card, and Digi 002 Audio Interface all working great. I think this motherboard supports only 2 usb 3 ports (which are in the back, on the corsair 500r I have 2 USB3 ports on the front, but I think the motherboard uses the back ports first) and seems to register the USB 2 Drive I have plugged in the back. I'll have to convert USB3 to USB2 inside the case for my front bay to work as it supports up to 6 USB 2 and 2 USB 3. Anyways, so here's what I understand so far (and hopefully it works for you Dquivilou):
To answer your first question, I loaded ML from my SSD (in safe mode or "-x"), then I downloaded Chimera 2.0.1 to my hackintosh desktop and installed to USB (may have to allow 3rd party Apps in your security settings). My assumption is that YES it does replace Chimera that's installed w/ MultiBeast (which again, is outdated... and is probably missing kexts/drivers/plist settings necessary for 10.8.3 to function properly with your system). I'm so glad that I kept up on this thread, because it saved me when I had to rebuild it... particularly these 2 bios threads:
Bios for Graphics Card (this is the one I used for this install, the big thing that caught me was make sure "Internal Graphics" are diabled if you're using your graphics card... skipped over this little detail).
Bios for Internal Graphics (Used this method the first time and it also worked)
Also, if you're still having problems make sure you started from optimized defaults in your bios before you start and try removing hardware that isn't necessary for Hackintosh to run(I removed my firewire adapter just in case, as I have one on the front of my system integrated into my Motherboard). I'm not sure what your build is, but I can confirm everything is working... also I disable internal LAN to get my wifi adapter working. I'll check back from time to time to see how things are going. Best of luck
*Edit: When I finished setting all of this up, I tried to do the multibeast settings and after booting from my SSD it showed the Apple logo and looked like it was launching into the OS, but hung on a grey screen. I went back and typed in GraphicsEnabler=No after selecting my SSD and it loaded just as fast as my 1st successful install. So then I went into multibeast and went:
Customization > Boot Options > GraphicsEnabler=No
Again... I'll be bringing this up to my standards for Audio Engineering and let you guys know what I come across for my build.
... restart, F12(or whatev), choose USB, and on Chimera screen highlight but DON'T click Enter unless you've typed -x (for safe mode) hopefully this should get you to the account setup and if you have a wifi adapter or ethernet hooked up you can hookup to your network and follow the steps above.