I am one of those fortunate enough to live in Maine. I do some volunteer work at the Boothbay Railway Village,
https://railwayvillage.org/and give shop tours to bus loads of tourists. Let me know if you will be here and we can meet for a personal tour.
The WW&F Ry in Alna Maine
http://wwfry.org/is spectacular. In something over 20 years a great group of volunteers have re-created 3 miles of Narrow gauge RR, with shops, car barn, turntable and just an amazing array of narrow gauge life. In process right now we are moving most of what was at the narrow gauge museum in Portland to Alna. Its not exactly a merger of the museums, but a very tight cooperation.
The Maine Maritime Museum in Bath
https://www.mainemaritimemuseum.org/ is well worth a visit. The usual museum galleries, plus the oldest Maine built wooden schooner, a small craft shop and lots more. They also offer tours of the Bath Iron Works, a shipyard building US Navy ships. The strangest ship ever seen, a 'stealth' ship is still on site- but I think the Navy will take it a way soon.
Send me a PM and we can arrange to get together if you are coming to the Mid-coast area.