I have no idea about your Buick dash, but I wouldn't think it would really be that hard to tell if it's welded or bolted. Once any kick panel trim is out of the way I would think that the hardest part would be getting situated to see from below/behind the dash with a strong light. If you don't see bolts/nuts then you're looking for spot welds, right? Have you checked with the Buick Owner's Groups, like the Buick Club? Buick Club of America - BCA - Welcome