Unfortunately, to do an HID retrofit, the halogen projector has to be replaced with an HID projector and that requires cracking the housing open.

I haven't looked into LED turn signals that much because I'm not planning on changing mine but it seems that to match the brightness of regular bulbs, an array of LEDs must be used. That often entails circuit boards so it's not going to be a drop-in replacement for the existing bulb and cracking the headlight housing open may be necessary.