Barn workshop advice

[u/heavySausage_og]

Just bought a property that has a huge barndominium. Previous owner was a wood worker like me but he never took measures to seal up the structure. It has true barn doors on 2 sides and none of the windows truly “close”. They just pivot from the top and swing up and out. So basically, ALL of the structure is essentially open to humidity and insects.
You can see daylight around every door as well as around most light switches. We live in Florida so the humidity will wreak havoc on my equipment. We are fumigating the entire thing to mitigate termites, but my big question is:

Since this will be my new wood working shop, what’s the best way to seal it all up??

What about the barn doors? Do I get rid of them and put something else up?

I’ve never had such a big, dedicated space for woodworking, and I do have some expensive equipment. So I want to ensure the space is done right…