Get some decent fluid (rather than using distilled water mix) and it should have very low electrical conductivity so a leak shouldn't be a problem unless your unlucky...
Also most kits will need some distilled water which isn't usually shown in the requirements... infact most of the "ready to go" "just 8 screws and your done" watercooling kits I've seen are anything but ready to go... you will need to remove your motherboard to put in the backplate, cut/measure the tubes, clamp them with whatever system yours uses (make sure you do this properly), fill/run it out the case and then top up, etc. which usually requires jumping a powersupply...
Unless you go for some fairly advanced kit I'm not convinced of the benefits personally - I got just as good results as a sub £100 all in one kit by lapping my CPU IHS and the bottom of the heatsink, maximising airflow and some AS5 properly applied... (tho the water cooling setup doesn't spike to as high temps on full out orthos)