Does anyone have a part number or know where I can get that panel that's under the steering wheel that has the trunk release button on it?

 

I can't seem to find the part number. But I searched on eBay and GMpartsDirect and it's under "column cover." On GMPD, it's going to run you a little over $100. Not the greatest bargain. I'd try eBay or even salvage yards before going with them. Unless you want brand spanking new, which you could even try to find on eBay.