Theres a guide on here to show you how to do the tortion bar, better if you know someone who can help you with it, its not that hard, but it is a bit of a b*****d to get right.
On a car of yours age you may be better to buy a deal with new shocks and springs together, as the lowerering springs will accelerate the wear on your shocks.
in answer to your question, its the springs that dictate the ride height of the car, the dampers just control the springs so your not bouncing - so its the springs you have to change at least.