I've had 2 liquid cooled rigs. One was a socket A rig with a cpu/gpu loop, and the other one was an sli gpu/chipset/memory loop. Always build your system from scratch, as you will see much better results as apposed to prebuilt kits. Prebuilt kits usually use tiny tubing and low quality pumps. You should look into dangerden for highend copper waterblocks, and I reccomend 3/4" tubing, hower 1/2" tubing will work well too. Maitenance isn't too bad, as long as you keep your coolant properly treated (ie if use use tap water [which is bad], or distilled water, you will want some form of anti algae mix, so you dont get crap growing in your loop. As for tubing, I'd go for Tygon if you can, however most aquarium pump tubing will work fine.
You are going to want to have a good deal of space in your rig, and your wires should be well organized. You dont want to cram in tubing, as this creats tiwsts and bends that hurt/stop the flow. Make sure you use a solid thermal grease from a good company like arctic silver. etc. etc.
After you pick up all the waterblocks you need, and you have your tubing, you need to pickout a reservoir, a pump, and a radiator. The radiator is critical, as it is what exchanges the heat from the liquid, and cools the loop back down. Radiators come as small as 120x120, however, I reccomend a triple 120mm setup. You probably wont have room in your case unless you have a good full tower/server case. In that case, just mount your radiator on top. For pumps, Dangerden has a few solid ones to use. I'd get a large reservoir, as it allows you to add more coolant without adding air bubbles (your worst enemy) into the loop. You will have to check your fluid levels/flow monthly, and I reccomend bleeding the system and refilling it every 6-12 months. If you have alot of money and some solid equipment, you should also consider phase-change cooling. Vapochills and Prometias are the most common units, but I've only used Vapochills. (vapo's also go better with lianli cases--some vap models can be bought with a special case that mounts underneath your lianli [should you own one])
Just remember to test your loop in the case before putting all the parts in. With regular testing and maitenance, liquid cooling systems are great.