-is it hard to setup
No, just take your time, and it's easy really. Looks hard and risky but if you do your research, it's a doddle.
-by leak test do you run the water while its away from the pc and just the blocks on their own on a table or something?
Some people do, personally I don't bother now as I'm confident in my building. I see little point in leak testing outside a case, to strip it down and then build it inside and leak test again. I will perhaps leak test for an hour or so if it;s something complex and I would deffo advise newbies to watercooling to do the same as a minimum.
-and when it comes to cleaning how often do you have to do it/is it a pain to do?
If you clean your parts right and use the correct liquids/additives your loop in the first place your loop should not need cleaning for 6 months-year.