Welcome to FISD Connor, if you haven't already, read this: Getting Started
1. Hero lenses are smoke-colored or green, but stunt helmets have green lenses. Most of the time people use either green plastic film (movie accurate) or welding shield. It looks darker than it is, but they are green.
2. All vendors sell helmets and you can buy one separately from the armor.
3. Look at www.starwarshelmets.com to get a feel for the different helmets: ANH, ESB, and ROTJ. Your helmet will also dictate how your armor turns out (or vice versa) if you are looking for 501st approval.
4. I don't have the skullworks set up but you should be able to find information by searching here. There are alternatives as far as installing fans on your own, and various members sell microphones and speakers, etc.
If you have more questions, keep asking them.