A lot of auto stores carry "Dye" for the plastic trim parts inside the car. What you really need to make sure of is that you clean the plastic parts really good. You'll need to remove the old Armor-All and stuff like that. If you don't prep really well you'll end up with "Fish-eye". A good de-greaser and then, for me, use soap and water and then steel wool and test the surface to be sure that the silicones are gone.
Most of the "New" repop plastic parts for the interior come black and you have to dye it to the correct color. It is just like paint. There is a top coat that also needs to be applied, can't remember what it is called. It helps seal in the color and helps to keep it from peeling or cracking.
After you clean really good use some steel wool to brush up the surfaces. For the dash I would not recommend that you use anything glossy. You could end up not being able to see out of the windshield if you do.
Here in Texas that is a really big problem. The sun bounces off the dash and the reflection of the dash is in the windshield and then the added glare from the sun. Hurts the eyes.
I redyed my dash pad from brown to black. To clean up prior to applying, I used a product called "Marine Clean" from the same people who make POR15. This cleans,degreased and really prepped the surface perfect. It will prevent the "Fish-eye" that ElkyPete was talking about.
I then applied a product called "Molecubond Color Refinisher" http://www.bryndana.com. I applied it doing many light coats, so the grain will show through. It came out pretty good, except it took more cans than I had thought. I guess there is not as much "color" in the cans as needed. If I had to do it again, I would look into some kind of vinyl primer before applying the final top coat color.
The dash is black and when outside in the sun, gets quite hot. So far, it has held up. No peeling or cracking. It even takes Amorall well.
Any product you purchase, I would buy an extra can or two, for future touch ups.