forcifer

1: not much as long as you double check everything and take your time. leaks are very rare and even then rarely do damage so i wouldnt worry

2: 10-100: doesnt exist outside of home made
100-200: super iffy kits, generally not that good. i would not recomend
200-300: somewhat better kits, still not the best but i would recomend for budget
300+: now we are talking :) super high end, super quiet, very good cooling

3: the fan on the radiator is generally louder

4: swifttech is ok, d-tek and EK are great, and for rads feser is the best. pump is laing