Start with LGA775 . Look for a Biostar TPower I45 , Asus P5K series , P5Q , Gigabyte EP45-UD3P these are a few good overclocking boards for LGA775 . A good 700Watt power supply is good enough . For LGA775 i would not bother to do any videocard benching , just focus on CPU clocking at beginning . Is a learning curve and it's better to take one step at time .
For a CPU pot you have a few options : Marksman, Kingpin, EK , Piotres or der8auer . Don't cheap out for the cpu pot , buy a good one in first place and you will be good . As for insulation there are a few guides in this forum that will help .