1. Depends if you work on it or pay someone to service it, and how you treat it.
2. No, think of a Series 2 V35 Skyline with a wagon body.
3. Bolt on? Not if AWD. You will need to modify a single turbo kit's piping. TT kits are not possible due to front driveshaft. RWD? Yes, same as V35/G35.
4. Like what? Unusually high water damage?
5. Feel free to use the search button for info regarding this and also for tyre/wheel calculators, You will need the rim width and offset.