LaRue,
OK, the 2008 E150 came with both Sealed Beams (on the base model) and Halogens on the XL and XLT models. So the easiest way to tell for sure is to examine the headlights and determine if the lens is glass or plastic. The glass will usually have some small bumps from the molding process on the surface, and you can tap them lightly with a key and you will hear a very distinct hard crisp clink of glass. Plastic lens are smooth, with no molding bumps, and if tapped with a key they will have a dull thud. Also, you can press on the plastic lens and it will flex a little...a glass will not flex
If you have plastic lenses, you need an H13 halogen bulb and the bulb is replaced through the back of the headlight by twisting the bulb socket to pull the bulb out the back of the reflector, and then you can twist the bulb out.
If you have glass lenses, you will need to remove the headlight trim bezel from the front and there will be a couple of screws that hold the bulb retainer/frame and you can pull out the bulb and pull the bulb socket straight out the back (don't twist).
...Rich