A few questions about refinishing a dash

I believe the plastic is polystyrene. I would try testors plastic model cement on the cracks. Be careful where you get it cause it actually melts the plastic. Any kind of plastic body filler for the marred surfaces, but sand the area with 60-80 grit sandpaper so the filler has something to stick to and grip. Again testers filler. You can shape the filler by white glueing sand paper to a paint stir stick. Sticks can be cut to any size or shape to suit/reach specific areas. Don’t forget to prime with a high fill primer before you paint.