I have completed a model of a drum set and due to the complexity of the model I believe I will need to set up render passes/layers to render. Now I figured I could just do something like render all the drums on 1 pass/layer and then render the cymbals on another (or really whatever combination works) and eventually just comp them together. Couple questions:

1) These objects are made up of very reflective materials. If I am rendering objects on different passes/layers, then won't the reflections (and even shadows) not show up when they should? For example, the drums won't have the reflections/shadows of the cymbals in it and vice versa.

2) To composite them together properly, due I need to render using Z-depth so that way the computer will know which objects should be in-front and which should be behind others? Or is there another option that maybe I am unaware of?

Really could use some help, would love to be able to get some nice renders of what is basically my first real high poly project. Thanks.