Im sure he'll come across this when hes not makin' money. But I think some sort of sticky/FAQ thing would be very helpful. Especially on topics like this where 90% of techs aren't certain on the material.
The NOx absorber is usually before the DPF, from what I've seen soo far. But near the back of the Motor ECS book under diesels, there are some picture lay out of the cats for diesels. Hope that helps. I'm a newbie myself also, trying and willing to learn.