1) I think that's a pretty good combination if for one who is sticking to the stock ride height. The Moog springs are better than the original Nissan parts and they don't have the sagging and bottoming-out issues, I've heard. The Bilsteins are a monotube design and have been proven to be a good choice on the R51.
2) You shouldn't need any additional parts, assuming all of the bolts and nuts come apart okay and don't need to be cut off, but a good visual inspection should be made just to be sure. Occasionally, The control arm bolts will seize to the sleeves inside of the bushings, meaning the bolts will have to be cut and replaced and either the control arm or it's bushings will need to be replaced, as well. You really don't know until you start disassembling.
3) No, but you will need to put a jack under the control arm to support it. As you lower the jack, the tension will decrease on the spring until you can remove it, and vice versa. That said, you should always be careful when dealing with loaded coil springs.
4) I'm not sure what you are asking, but all bolts have a specific torque range as specified by the manufacturer. Make sure that when you tighten bolts that go through control arm bushings and such, the weight of the vehicle is loaded onto the suspension. In other words, don't have the vehicle jacked up on the frame with the suspension hanging when you tighten suspension bolts.
5) Loctite shouldn't be needed on any of the rear suspension bolts.
6) Yes. Anytime you change any suspension part you should get a four-wheel alignment.