If the retention screws allow, install the fan onto the cooler BEFORE you mount it to the motherboard. And mount it to the motherboard before you install the motherboard into your case.
In my case, the special bracket for my 1156 socket type requires that I install the cooler to the board, before I can completely mount the cooler. It's a bit more difficult that way. But if you mount the cooler to the board, then the fan to the cooler before you actually put the motherboard inside the case it's not too bad.
As for thermal paste, I'm using Arctic Silver 5 (AS5), which continually gets very good reviews from test/benchmark sites.
The guidelines I would personally follow with i5 / i7:
1) Keep 100% load temperatures @ 72C or below. Real gaming and such won't push your CPU to 100% on 4 cores, so you'll really never hit that high during use. However, use Prime95 to test stability and max temps.
2) Don't exceed 1.5V or CPU voltage (someone correct me if I'm wrong for i7). Lower is ALWAYS better, as it reduces temperature and CPU wear n tear. Too high of voltage can shorten life, or if taken too high can ruin the CPU.
3) Stability, stability. As high as you can go speed wise, with safe temps, and keep it stable. 4Ghz seems to be attainable with Air Cooling, and much over that you probably won't see a whole lot of difference with mundane activities.
Actually, the HDT-S1283 is #6 on the Frostytech temperature list. That's the original version. The Dark Knight is the new Nickel Plated version. Essentially the same unit otherwise.
My booboo....I was trying for 4.4 Ghz and running OCCT when i was checking .... when OCCT is using 100% CPU cycles, screen rendering slows to a crawl sometimes.....when I scrolled down the Prolima was sitting on top of the #6 image....thx for correcting.