First question... it's just a ring of light. A halo if you will. They're usually pretty dull/dim and only act as like daytime running lights as a cool effect.
The HID will pretty much drown it out as far as light output goes...
To get them, you have to open up your stock housing and mount them in there. There's "demon eyes" or "angel eyes" whatever kits on eBay for the FX, but I don't think anybody's tried those out yet. They look like they'd be a huge disappointment to me, but saves you a lot of work (I don't remember reading if it's the kit to open them up and DIY or if they come completed...)
As for the second question, you can do it yourself. Just get some VHT NiteShades spray on tint and read the directions. Maybe practice on some clear plastic or plexiglass or something first. I plan on doing this very thing myself and black out my red tails so I can have a changeup between the clear tails and blacked out tails.
