DISCLAIMER: Because the 350z is a specialty car and they don't sell a lot of them, I only have experience with maybe a half-dozen. But the elecrical system is the same on most Nissans.....G, Maxima, FX, Altima.....and I've worked on plenty of all those.
Anyway,
1. XK02: I never saw much value in this product. There's already a way to control the locks without splicing or running wires into the doors:
http://www.audiogroupforum.com/csforum/showthread.php?t=10529&highlight=Nissan
2. 530T: Useable but unnecessary. On your car, if you simply apply extended pulses to the lock/unlock wires, your car already has a factory feature to roll the windows up and down.
NOTE: The doorlock method mentioned in #1 does NOT do the windows. You need to run the wires into the driver's door, which isn't even very hard on that car. Also, the XK02 doesn't control the windows either.
Go to the link in #1, go to page 4, for a little more information on window control.
3. XK07: The manual could stand to have a little more information.
The car's pink and blue CAN wires are not easy to test, but they are easy to find. They're in a corner of the plug at the BCM, and are a twisted pair.
If you connect the XK07's data wires incorrectly, it simply won't program. You won't break anything.
The pink and pink/white wires go to a small relay inside the XK07, and their purpose is to interrupt the wire going to the car's security LED during remote start and after key takeover.
You could actually not even connect the pink and pink/white, and the system will work 100% fine......but the security light on the car would stay on until the end of your trip.
If you find it any easier.....the OBDII diagnostics port under the driver's dash also has Constant, Ground, Ignition, CAN H, and CAN L.....you could hook the XK07 up over there if you like.
The security LED wire you'll probably just want to get at pin 38 of the BCM as listed in the guide, but you can also go right to the security LED directly if you want.
TIP: You wanted to know how the wires would test.....turn the car off, remove the key. The security LED wire will test as a brief ground every time the LED flashes.
Also, when you do go to cut the wire in half on the car, verify that the LED on the dash stops working. If it still flashes, you cut the wrong wire.
4. Windows control using factory Nissan wires. Yes, as KPierson says, just connect one wire to the lock/arm wire in the door, another to the unlock/disarm..........and run those two wires into the passenger compartment.
You'd then connect your Viper's lock and unlock wires respectively, but also splice on some AUX channels from your Viper......but if you make these splices, say, down in the kick panel, it makes future changes/repairs much easier and neater than if you ran a bunch of wires into the door.
5. Violating factory wires. There really aren't that many wires you'll need to connect to anyway. What do we have? Parking lights, brake, trunk, domelight (you can use the car's "domelight supervision" wire as your door trigger), trunk pin, maybe tachometer (but it's under the hood).......and your six main wires at the ignition switch.
The most challenging connections will be at the ignition switch. There's very little room to work, the wires are very thick, and you have to make good, reliable connections.
After that, you'll find splicing in the brake and parking light wires to be easy, and almost non-intrusive to the car.
If you really do want to avoid adding wires to the car, look at idatalink products. Their module gives you door trigger, brake.....and a bunch of other things that the competition doesn't. Just go to idatalink.ca, put in your car, and look at the install guides.
6. D2D. Don't worry, you're not missing much. I think the marketing department worked very hard on the D2D concept....it's too bad the engineers didn't. It works about half the time, it's poorly supported, and they don't seem to be making too many apologies for it.