Wish I knew of a good shop up that way. Sad to say I don't. Maybe someone else local can chime in.
There's a solid Nissan presence in Nashville. If nothing else, you could probably ask around at one of the Cars and Coffee events at the movie theater off Cool Springs Blvd (exit 68, westbound off I-65). They're every Saturday morning, but the first Sat of the month is the big meet. Lots of Z guys turn out.