Some of the labor quotes look a little outrageous IMO. 7.5 hours for a clutch for a Z specific shop with full power tools and a lift is stretching it quite a bit. 2.5 hours on a BMC is borderline ridiculous; I can have mine switched out bleed in less then an hour and a half. The quote for the injector replacement is laughable, no way should take 7.5 hours to do that job even with a plenum pull. All of the other quotes are standard NISSAN pricing and look to be pretty accurate. It seems the labor category is where you may be stretching your wallet a little thin; but at least you'll know it's done right and have peace of mind knowing that ZCG will stand by their work.
And you can buy a new Labree/specialty Z cat back for that much:"The "Basic System" starts at $750 and includes aluminized piping with an x-pipe.