No, you will not need all new graphite parts. You can upgrade you car to the graphite as you see fit...all parts are interchangable. If you are a decent racer and what the added performance of the graphite parts, I would suggest buying the graphite kit for the TC3.
Graphite, while lighter and stiffer, is also more brittle. In theroy, the lighter weight and stiffness of the graphite will allow your car to be faster and more responsive. You may not even be able to tell the difference between the 2 materials when driving your car.
If you are a beginner, stick with the normal composite materials. They will take more abuse at the track and are less expensive.