Diesel fuel smell in cab of TDI Golf

Hi Folks,
Just hoping for some support if you don’t mind. I have a 6 year old 77 TDI Golf Mk 6. For the past 6 months I have noticed occasionally (maybe once a week) a strong diesel fuel/smoke smell in the cab of the car when I’m idling at a set of lights. It’s so bad that I need to wind down all the windows to breathe fresh air until i drive off and makes me feel sick. The engine also revs higher at about 1200 rpm instead of being around 750rpm at idle. I took my car in for its yearly service last month and the dealer mechanic said “the diesel particulate filter gasket is breaking down and needs replacing” and they were adamant that is what’s causing the issue. Does this sound reasonable? Has anyone else come across this before? I have booked my car in next week to get it replaced ($400 including labour), I don't feel it's safe to my health leaving it any longer.

Coincidentally, my Golf is caught up in the “Dieselgate” stuff with VW but i don’t know if it’s related or a separate issue.

Thanks so much for any thoughts and opinions. Cheers.