If you select cat'd bolt in you won't have to do any welding and could install it yourself.

If it's going to cost you $100 for a u-bend delete don't bother. The stock dp is so restrictive that I don't see the point in just a u-bend delete, even on a N/A car.

For the exhaust manifold gasket, I've seen the stocker reused. But, to me it's cheap insurance to get a replacement to avoid having to do it again.