The stock harness will not safely work with these bulbs; you will run the real risk of burned wires and/or other damage to the vehicle. At least upgraded wiring and relays will be needed, but you don't mention what kind of car you have. Depending on that, the bulbs you bought may or may not be safe to use even if you install adequate wiring and relays.
Whoever said that is wrong. There are no original harnesses capable of safely supporting 100w bulbs or anything close to it. And you still haven't said what kind of car you have. Without that information, you cannot get an accurate answer to your question.