You should always ask for the parts that are replaced, and specify this BEFORE any work is done. I had to start doing this at the dealership I bought the car at because I suspected that work was not being performed.

The same mechanic confirmed that much of what the dealership said they were doing was actually not done.

So, they have not only lost a service customer, they (dealership) lost possible future car sales, and actually Nissan in general will not be getting any of my business.