Does this bolt straight to my stock exhaust system?

Yes. This is an axleback, so it connects at the factory axle location where your current rear section bolts on. No mid-pipe work needed.

Will this need welding or cutting to install?

No. It's a direct bolt-on replacement for the rear section. You'll disconnect the factory axleback and bolt this one in its place using the existing mounting points.

Does stainless steel require any finish prep or protection?

Stainless resists corrosion naturally. You don't need to paint or coat it. Just install and let the material handle the weather.