Unfortunately the servicing dealer will not except liability, but what I am saying is that the missfire may be down to "bad" servicing so this should be looked at this first. ie: plug issue, coil pack issue, wrong grade/viscosity of oil which may be effecting the operation of the VVT.
Before you start phoning around for prices, I would highly recommend that you get the car to a 350Z VQ35DE specialist for an informed diagnoses on the fault.
I have plenty preowned low mileage VVT sprockets etc. in stock so that will save you considerable cash if they are required, however the teeth are not prone to wear on the sprockets.
Regarding oil consumption, only you will know how much oil you are having to put in every 1000 miles.
With respect, you are putting the cart before the horse, so unless you have money to burn, best to get a proper professional diagnoses from a specialist, which can be done without removing and stripping the engine.
Regarding the chain kit, I can send you over a link where these can be purchased.
Alex.