Check out the forums at these sights:
[H
Overclockers.com
OCs.com also has a really good articles section on watercooling.
Now to really answer your question, I haven't actually had direct experience with watercooling, but I have been researching for quite some time. I should have my rig WC'd within the next week.
I don't think it's necessarily *that difficult* to setup, but it is more involved that just slapping your heatsink on. Expect to spend at least 30-45 minutes bleeding air and making sure everything is OK. Then let it run a day or two outside the case to check some more.
The maintence is probably about that of aircooling. About as often as you'd clean dust from your heatsink, you should check the system for bio-growth or corrosion. Water shouldn't need changing except once or twice a year.
Hope that helps.
