I worked at a living history museum for a number of years where I worked in two of the parks time periods, I then did some reenacting, French and Indian War, American Revolution and War of 1812 so all well before you're time period ST. I've also had an interest in WW II for years and there are/were several kits I'd like to put together. I've thought those helmets from the Big One were cool and have wanted one for quite some time.
Thats pretty cool about the living history and reenacting. Did you have to come up with your own uniform for the reenactments, or were they provided for you? I would think repro uniforms of that time period would be rather pricey. When my wife was younger, she volunteered over at a local museum, which has a village as a part of it. It wasn't technically living history, but she would dress up as a pioneer girl and run around the village. She enjoyed it immensely and, to this day, could talk about it for hours. I wouldn't mind seeing some WWI reenacting, but the closest ones are several states over. I haven't shopped around for WWII helmets much, but if you look around, I think you could find some pretty decent repros for a good price.
When I worked at that living history museum you were provided clothing/gear but over time I started buying my own. There are places where you can buy clothes but the authenticity varies. I had some stuff made by people I know who I know do good work and is authentic, and yes it can be/was pricey.
Once there was a WWI encampment about an hour away at a historical society, I went there and of course they had already packed up and left for the weekend (early).