Total time actually welding he spent about two-three hours. Prep (removing the manifold, batteries, and waste tank, and preping the area for welding) and getting in and out of there about 20 times it took about 10 hours.
If I didn't know him I would have probably just used JB weld by its self. With some really good prep work and an aluminum plate larger than the hole I think the JB weld would have held just fine.