How many miles on that car? Do you have a garage to work on it during the winter? If not, get her a good waterproof car cover for sure. Hows the trunk and floor pans? Does the engine knock? Id hook up a GOOD engine diagnostic tool (like turbo link or directscan) and see what its doing. after that, id do a leakdown/compression test, and cut the oil filter open, and check out that oil, then send out that sample for an analysis. I'm suggesting all of this, because if the engines still ok, and it doesnt appear to be close to blowing up like a bomb, I'd progress further. But if it fails its leakdown/compression tests, you know to yank it immediately, and find a good builder close to you. that way, you can have some alone time with that body in the winter, while the engines being gone over.
And all that white in the picture, is that bad checking, or just oxidation. Before you have that body media blasted, I'd buy a nice buffer, and use that paint to experiment first, before they blast it all off. (unless youre already good at that stuff) I never turn down an opportunity to experiment. Those rims can be cores for Gbodyparts.com rims too. Good luck with your project and welcome to the world of Buick, the leaders in speed and luxury.