I have a '78 that is black/black too. The chicken head switches between two full rich sounding settings and two really thin, useless settings, for four total. The good ones are not togehther -- it goes good/bad/good/bad ..or bad/good/bad/good (depending on your perspective). You'll know when you hear them.
The three knobs are volume (top), bass(bottom) and mid/treble (to the right), if I remember correctly. The mid/treble doesn't work quite the same as on a Fender P. It doesn't dial in a lot of highs, its more like high mids.
One of the two "useful" chicken head positions will give you a slightly darker, deeper tone (the one on the end), while the other will make it slightly brighter (the one in the middle).
There's no direct pickup selection available. The chicken head switch decides what its going to give you in that sense.
Rippers are great - they look badass, and are fun to play, with the thin body, and imo, relatively lightweight. They can be a little bit neck-heavy, but I put Hipshot ultralites on mine and it balances beautifully with them.
Gibson just re-issued them only in natural, at a ridiculous price.. even street prices are exhorbitant - between $1,900 and $2,200 - depending on where you look.
The re-issue has two more positions on the chicken head (for a total of six), and the electronics are a bit different. I'd love to hear the kinds of tones you can get with it.