As DG said, Vectra C diesel manual covers the DTi.
Do not disconnect the swirl valves. Clean them and ensure they work properly. With them removed, there is some experience of throwing EMLs because the air flow at low revs exceeds parameters. They are also there to make the engine work more efficiently.
However, do not just clean them, but clean the rest of the pipework too, there's no point cleaning the end of the system if everything before it is still filthy. If the EGR is also at fault then that may have to be cleaned, replaced, blanked off or mapped out for the problem to go away completely.
I hope your mechanic does the job as thoroughly as we would with our own cars. Oh, and just because you are a woman doesn't mean you can't get stuck in if you want to.