If you go HID, you need to make a wiring harness so that your stock sockets are only triggering a relay, and the main power comes directly from the battery. You'll be safe running halogen projectors from your stock sockets, but i'm not sure if halogen projectors are made to use the same bulb attachment from your truck.
There are usually "plug and play" units available on ebay for many makes and models....they're pretty much all garbage. It's definitely worth spending the time on your own to do it right.
As Adrnln Jnke entioned, the retrofit source is great for parts. The guy who runs the store gives great customer service, and will personally call you to discuss your needs and what he can do to help.
here's a Pic of mine
<a href="http://s35.photobucket.com/albums/d189/mjs3350/Vehicles/Sport%20Trac/?action=view¤t=P5230024-Copy-1.jpg" target="_blank"><img src="http://i35.photobucket.com/albums/d189/mjs3350/Vehicles/Sport%20Trac/P5230024-Copy-1.jpg" border="0" alt="Photobucket"></a>