You may be slightly confused about the difference between an HID conversion kit and an HID Projector conversion kit. Both are true HID setups, but one using a standard headlight lamp while the projector uses a true projector with cut-off to provide a crisp, concentrated light out put. Here is a picture of a true projector HID conversion:
The first image is an HID projector cut off line. This can only be acheived using a projector. The second picture is an HID conversion kit with no projector.
HID Projector set up.
HID Conversion kit without a projector
So how hard is it to do a projector set up? A lot harder than a simple HID conversion kit. You will need to customize, or retrofit, your new projectors into your existing headlight lamps (usually requiring you to dremel, glue, and modify your headlamps).
Also, be aware of products that claim to be ‘projectors’, as there is such thing as halogen projectors. From experience these set ups are terrible. The one I saw on a BMW was a complete waste of money, with probably less output than the original halogen bulb set up. Go with the true projector hid conversion kit, don’t waste you time with the halogen projectors. If your budget is around $100 and require only an hours worth of work, buy an HID conversion kit.
If you have $600+ and 6+ hours of time to spend acheiving the projector look, an HID projector retrofit is for you.