I agree with SILVIA-S14.
Seeing as Z Fever specializes in Z cars, they probably do the best job as compared to a Nissan in general shop or something.
What does the $5k include? Everything? In all honesty, that isn't bad at ALL. With the amount of work you know they'll be putting into it, that's not exactly an arm & a leg.
So unless you can find some friends to help you out and get all the equipment and parts that you need on your own, I doubt you're going to find a better deal around town.