Where to buy Buick parts?

Where is the best place to buy original Buick replacement parts? Online? Brick and Mortar stores?

How do you all feel about third-party replacement parts instead of genuine Buick replacement parts?

I generally try to stick to Delco for the importants, such as engine parts and filters. I use havoline oil, delco trans fluid, Trico Winshield wipers, and Michelan X-one tires. I'd stick with Delco if I were you, the parts are actually engineered for the car.