Unfortunately, you can't export to dts with SketchUp. But since you have SketchUp Pro, you can always do the following:
1. Export your model from SketchUp to an .obj file. It's a commonly used format, all 3d modelling programs should be able to import it.
2. Get a 3d modelling program capable of exporting to .dts. There are two common options here, Blender and Milkshape.
3. Rig your model in either of those programs
3.1. Add mount points for the driver and the passengers (mount0, mount1, ...)
3.2. Add mount points for your wheels (hub0, hub1, ...)
4. Add a collision mesh for your vehicle. It's important, otherwise you'll keep going through walls and stuff!
5. Set up the exporter
6. Export
This is just a general workflow of getting things done, by no means this is a complete tutorial. For more specifics you can always check out the General Modification Discussion board. There should be plenty of tutorials or other pieces of information about exporting and working with Blender or Milkshape. I hope this helped a little!
