Hi Again Ph0eniX,
You don't have to. It may take a while but you can ski shaped skies using straight ski technique. I still do it all the time and many of my skiing friends ski shaped skis and insist they haven't changed anything. If you buy a shaped ski designed for bump skiing it isn't nearly as radically shaped as others. GS skis also tend not to be as radical.
One of Whiteface's top instructors told me about carving twenty years ago and said unweighting were not necessary to turn your skis. He was definitely ahead of his time. He also told me there is more than one way to get down the mountain and turn technique varies with the terrain. My shaped ski-carving instructor insisted that no skidding was allowed. The head of Whiteface’s ski school had me (during that same year) practicing skidding my shaped skis down the mountain. He also insisted there is more than one way to get down the mountain. My skiing philosophy is to try a bunch of techniques and use the one that is easiest for the terrain and conditions. I think it's good to have a "quiver" of techniques as it's nice to have a "quiver" of skis.
What really matters is being on a mountain and having a great time. My youngest daughter raced for years and used to get on me for always thinking about what I was doing and working on technique. In her words she said, "stop thinking, just ski." Her words reminded me of a Yogi quote, "How can you think and hit at the same time? How can anyone argue with Yogi?
You can see Yogi quotes at:
http://adkron.bizland.com/yogi.html