Going to buy Z in September. Need help.

[BeksNice]

Hello, guys.
Since, I know nothing about Z's could you please answer a couple of questions?

First of, the reason why I'm going to get Z in September is because I will be out of country during the summer.

Question 1.
Will it be worth buying 2010 370z with (let's say) 15k~ miles on it? There were some arguments with my cousin that cars like Z will require a lot of maintenance after 3-4 years of usage. Is it true? I don't really want to spend $33k~ and then drive around trying to fix it, if you know what I mean. (I never driven a used car before though)

Question 2.
I want to get vertical doors on it installed. Will it break the warranty? Where will I be able to have it installed in LA?

Question 3.
If the car won't come with built-in navigation package, is there anyway to get it?

Sorry for some grammatical errors :d

And thanks in advance for help.
Best, Beks.