Do I need to weld this kit together, or does it use slip joints?

These are individual sections designed for welding. You'll need a MIG or TIG setup to join the pieces into a complete system. Slip-fit assembly is not part of this kit.

Can I bend these tubes myself if the kit doesn't have the exact angle I need?

Mild steel can be bent, but it requires a tube bender or access to one. If you don't have the tool, a local muffler shop can bend sections for you. Test-fit before welding anything in place.

Will I need to prime or paint these pipes before install?

Bare mild steel will rust if exposed to moisture and road salt. Plan to paint, ceramic coat, or wrap the finished system after welding and before installation. Raw material ships unfinished.