Sbeall, this is great!
What have you done? What have I done leading others down this path!
At least you don't need to put all the hundreds of 3D modeling hours into it. I spent the greater part of 3 summer vacations to get the bulk of it done.
But don't worry, you can do it.
The payoff when you can hug your finished space helmet like I did and then the joy of showing it off to friends is priceless.
I actually decided to upload all the stl files I have now to Thingeverse or eqivalent service.
I can update them over time and re-release if needed later. I'll start looking over my files this weekend.
Probably... Home sick with the flu now so I can't concentrate to do it now, no energy.
Since I use insert blocks that need sanding smooth and use real screws and rivets as well as drill and tap some holes manually it's some DIY work to assemble. But it's not too complicated. Lining up holes on the helmet and adjusting the lighthouse to be straight was the hardest part, I just did it by eye but you can use measuring tape and mark it up to make it easier.
If the block system is getting too hard to use I can merge it all in my cad system and only have a couple parts as inserts. Won't look as good finished but it'd make it far easier. But give it a try.
You could start with the sub blocks for the ear pieces like I did to get the hang of how it works. Most pieces are pressed in place in slots, some are screwed in place.