1) what kind of power supply do i need, like how many watts? and what brand? i heard corsair is the best.
2) what is the best heatsink i can get to run this i5-750 at 4.0 ghz stable? (i would play WoW many hours at a time, nerd huh? )
1) I consider Corsair, PCP&C, Seasonic, Enermax, OCZ and the Antec Earthwatts line to be the best PSU's available.
With your setup, I would recommend a minimum of a 450w PSU and AMD Recommends a 600w+ PSU if you plan on CrossFireing your 5770 in the future.
2) FrostyTech has a good listing of the Top 10 CPU Coolers which would probably be a good place to start.
JSC has a few good ones listed, you will probably need to list your budget so we can narrow it down a little more.
If you have the budget and some extra time to set it up, water cooling is an excellent alternative.
Swiftech makes a great kit to get you started, currently $230 on Newegg.