I've done alot of write ups on this. If you go to Team SR's board, and do a search for Airbags, you'll find a Looooooooooong post that I did entitled "Everything You Ever Wanted To Know About Air Suspension."
It basically gives you all the info you could ever want on this type of suspension set up. But to answer a couple of your questions, there are only a very small handful of companies out there that offer air ride kits for Korean vehicles. Some of these kits are weld on, and others are bolt on. The kits that I offer are strictly bolt on, so in case you ever want to go back to stock or regular lowered spring suspension, it's real easy to do so.
As far as what Tigger said...it depends on what kit you get as far as suspension rigidty. The air bag kits are not good for drag racing or auto-x....but the air rods kits are ok. I'm currently working on some new designs for a new kits that willl allow you to either auto-x or drag without a problem. These will be full Fast Air "Rod" kits. I'll have kits for Accents and Tiburons, and so far I have 2 people who are coming to my place to be guinea pigs for both kits once the final prototypes are finished. If everything goes as planned, I should have these new kits finished by early part of next year, and then I can start working on getting kits for the Elantra, and Sonata.
Guilty...you're basically right with all the parts. Except, the parts you mentioned are standard products for an air bag kit. It's almost identical to the "Rod" kits...just a couple of small differences. Also, with my new kits..there will be a special little manifold for the front and rear that will montior the air in each rod. Any time the rods start to lose air from drag or auto-x, the manifolds will automatically keep a constant supply to the rods so that they don't lose air, and therefore, not allowing your car to sag to one side or the other. There's a bit more into it, but you get the idea. <img src=icon_smile_big.gif border=0 align=middle>
Anyone that gets a normal kit, they can watch the air pressure in each bag or rod by installing a set of PSI gauges to watch the air pressure on each side. If you start to auto-x and you notice one side getting softer, just air up a little and you'll be good to go. However, there will be alot of body roll with bags no matter what you do. The rods are the best if you decide to go that route (auto-x) other than show.