Have you seen my guide? :o
That said, answers to your questions -
1. If you will OC your i5, i5-3570k + Z77 board like ASRock Z77 Extreme3, if you won't, i5-3330 + B75 board. i5 already performs excellent without OC, OC is just an icing on top.
2. Intel HD graphics is irrelevant in this situation. I am not sure why Intel continues to throw in top-end integrated graphics in an enthusiast CPU -- no enthusiasts will be using integrated Intel graphics except in a pinch / troubleshooting / emergency anyway (like your dedicated GPU died or something).
3. Go with ASRock Z77 Extreme3 instead. The Z68 version of it was pretty damn popular, and this will continue the trend, I'm sure.
4. If you will not OC, you don't need a 3rd party CPU cooler. Otherwise, Hyper 212+ EVO is a great cooler. Ignore anyone who says otherwise -- it's something else that is causing it to not perform very well.
5. GeForce GTX 550 Ti is roughly equal to HD 6770. This would still have granted you a good boost from HD 4650.
What you didn't know is that WoW is very demanding on CPU. If your CPU is old or weak, no graphics card in the world will save you from having crap FPS in raids. With an Intel i5 CPU (overclock or not), you should see GTX 550 Ti finally working at its full extent in raids.
If you game at 1080p resolution, I would recommend replacing GTX 550 Ti with something more beefy like HD 7850.
6. Is this 80 Plus certified, with 2 6-pin PCI-E power plugs? If so, you can keep on using it. Otherwise, I recommend a 500W ~ 600W (depends on how powerful of a GPU you plan to get), 80 Plus Bronze certified. IE) PC Power and Cooling Silencer MK III 500W. Modular is a big plus too nowadays.
7. Corsair Vengeance RAM modules tend to come with tall heatsinks that may interfere with 3rd party CPU cooler fans. Performance-wise, they will be more or less the same.
8. HAF 912, but that's just me.
9. Samsung 830 is good, can't go wrong.