you can buy pretty much prebuilt kits, from Asetek, your locals should stock some of their kits (I'd link, but I don't know which country you're in ). I use a koolance ATI cooler for my card, and that gets to a max of 60 degrees load, overclocked to 600/600 from 400/490.. It works really well, I've not used the Nivdia version but I assume it's of the same quality. Only downside is the tubing size, but hey. Can't have everything, and converters can be obtained from water cooling specialists.
Water cooling does have slightly better cooling capacity than standard fans, but to get the same level of cooling you're going to want a dual 120mm radiator with some Yate Loon 120mm fans. My personal favorite radiator is the Blackice series, but that's just personal preference, I advise doing a lot of research into it before you make the jump, that's usually peoples biggest mistake.
Most of the time water coolings biggest componant is the reservoir, which can be external if you so desire (Makes it easier to top up).
Again, the best course of action is research, measuring your case, working out the placement for things, getting the best bits you can afford.. I advise Hydor pumps, though. It might be best to buy the parts individually, instead of a kit depending on how you want to play it.