In terms of springs I'd look at getting a pair of springs + dampers that were designed to be used together (in terms of spring rate and dampening force) otherwise you may end up with a less than ideal ride. Also I'm not too sure how beefy the OEM Nismo struts are, but if you lower it too much you will prematurely wear out the struts.
Finding a decent set of coilovers that don't offer to harsh of a ride may be the best way to go. In terms of 370Z parts, I'm no expert as I'm new to the Z myself coming from an S-chassis world. I ran Eibach prokit springs on my S14 and was pleased with them, although if you're looking to slam your car to the ground you'd have to go with a different spring. But really, be nice to her and don't slam her into anything
Paint code should be able to be found in the door. Many people like the Stillen Gen 3 intake and I believe it can be used on the Nismo (correct me if I'm wrong anyone).