Setting yourself up for failure with that attitude
Reliability depends on the car you get. My Z cleaned me out, but that was due to me getting over excited and not having it checked out really well. Many have great success with their Zs reliability wise.
Honestly it's a very fun car. My car is swapped, but I drove it as an N/A for about 4 years. It doesn't do 1 thing perfect, but it does almost everything well. It has enough power to put a smile on your face, and can handle corners pretty well. The NA doesn't respond too great to power mods, an intake and exhaust, maybe a pulley, is about as far as most go engine wise. Putting money in the suspension yields the most noticeable results. And there is a fantastic community, both online, and in Ohio.
I would have it inspected by a good mechanic, member SilverTwinOH if you could, he's a bit of a drive south, but he knows the cars very well.
Also, don't buy an N/A if you really want a twin turbo. Too many people buy them, and immediately talk about swapping, and how they want a turbo. Make sure you can enjoy the car as an N/A, as it is usually cheaper to just buy a Twin Turbo if that's what you think you would want.
Check out 300zxclub.com and twinturbo.net. There is tons of info in the FAQs about what to look for.
As far as auto-x, Im sure aesthetic_influx will chime in soon, he auto-x's his.