2. You don't *have* to disable anything in BIOS, but maybe you should disable Cool n' quiet as it can cause unstability when OC'd, though most boards do it automatically when raising multiplier.
3. Look for a config that most people seem to be stable at, most people seem to get it stable at 4 ghz and 1.45v for the thubans(which is still safe), so go for that and test with prime for a few hours. It's not like 4.2ghz or more is gonna get you much at all other than heat and lesser lifespan, scaling doesn't do much even over 3.8ghz.
4. It should be fine, but you'll be cutting it close.
5. Prime 95 overnight ( 6+ hours) or lynx( that is a REAL "torture" test) for a couple hours or less, Do not pay attetion to the people who say less than 24 hours is not truly stable, that's only a waste of time.
This would've went better in the overclocking forum.
Either the TIM supplied with the HSF or Arctic Silver 5 will be fine and probably within 1 degree C of each other. You can even experiement with one and change to another later if you're into fun.
Disable C1E and Cool and Quiet in the BIOS. Follow the information in the links below. While you can try 4.0 GHz. immediately, it may just BSOD or not boot. Most people start slow and work their way UP instead of trying to work from some perceived OC down.
It sounds like you're new to overclocking so there is a lot to learn and you'll need to go slow and be patient as OC'ing is a JOURNEY not a DESTINATION. Your CPU/mobo/RAM are different than the next persons so what your hardware will OC to may be different than there's AND the BIOS settings you need to get the most from your CPU can also be much different than there's. Nothing in OC'ing is guaranteed so go slow and learn what your CPU/mobo/RAM desire for best performance and reliablity.