My thoughts.

This is nothing to do with being elitist & I accept that we all make mistakes but to replace an expensive DPF based on a description on a scanner (especially a generic scanner) is foolish given the apparent lack of knowledge about the functionality of the system.
As Dave has asked what was the thought process behind this decision?

I know we all have to learn but surely some investigation first would have been beneficial, we all need help at times.

Gerald, if I were you I would take John up on his offer of information. You could then refit the old DPF to see if it in fact faulty when you have the correct information & test procedures for all the components involved.

Steve