There are many older threads discussing the dashboard cracking issues in second gen AVs as well as Tahoes and Suburbans. early on you could get some help from GM under warranty but due to time now it's a matter of replacing from your own pocket with a dealer or buying a used dash upper from a junkyard.
Some have tried self repairs, others have bought aftermarket covers and applied them over dash, either in a plastic or fiberglass and then others have gone old school and bought carpet style dash covers and installed them over dash to prevent UV rays from deteriorating (usually over a new factory dash.)
You will find more info and photos in the older threads probably in interior mods section etc.
Good luck with your efforts.