I fixed one in the past using some plastex. Basically it is powder and a liquid. Mix them together and they chemically bond into plastic. You have a little time to mold it however you want. When you first mix it, its very running but soon thickens up. Once dry, it can be sanded/painted. Of course if your dash is completely broken, this isnt going to help.
I started with a cracked dash and then applied the plastex mixture to the top side. Once dry, I applied a thick layer on the back side as reinforcement. Then I sanded all my areas flat and repainted the entire bezel.
Dont get me wrong, it was a lot of work but I was very happy with the outcome. I sold the game soon after I fixed it so I can say how well it held up.
I attached a picture. The dash paint did not quite match the original bezel but it was as close as I could find. This dash was cracked by the start button, the bolt holes, and I believe both sides of the shifter.
www.plastex.net