I feel for you OP, but as other have stated I think it's a bit ridiculous. Not a lot of good can come from excessive paranoia causing us to make large changes. You're probably just isolated to your TDI but a little poke with the logic and we can apply the same paranoia and thinking to everything in our lives, sending us all to the grave ironically early.
What's the details on your Mustang? I'm sure we can scour the internet and find some ticking time bomb in those that is probably really expensive--I mean it's a Mustang. Point being, as the saying goes, "drive more and worry less."
And as a side note...I've enjoyed my dealer so far. The service manager has been nice, respectable, and they've worked with me on a few issues. I've gotten my empty oil jugs for them so I can at least verify they're putting the right oil in. It's a bit ironic when people claim the dealership's supposed trained technicians are always moronic and they instead go to local gurus working out of their back garage. Not to say I haven't used those gurus for other vehicles and in the time past...but blanketing all the dealerships as bad is a
very disingenuous service to new and worried readers.
And...I still get excited when I see a Mustang, man I want one!