We're tearing out and rebuilding a shower stall. I'm getting overwhelmed looking at plumbing fixtures (I want a showerhead, handheld shower, couple of body sprays) because I don't fundamentally understand how the plumbing works... mixing valves, single-control valves, all of that. I can't sensibly select and order parts if I don't know how it all works and what's the best arrangement. Can anyone recommend a good primer for me?

Do you have only 1/2" piping for the water? If so, you can not get the volume you want for all those gadgets.