chance of oopsing isnt that big
the thing about watercooling is you need a big case if you are putting somehting inside

components are expensive too
the only think that i see worth paying for is the pump and the blocks
as for the rad, i would go for a heatercore instead and get it from a junkyard for cheap or even free as long as it doesnt leak

heatercores can be big though and hard to mount inside a case
im planning to do some surgeries to my case if i can get my hands on a heatercore
perhaps do my own external kit but it would be non removeable and attached to the case itself