My understanding is that should you pick the car up in California, you must pay the California state sales tax.
And then probably the sales tax in Maine also.
I do recommend you schedule a trip at some point and take a tour of the factory: nothing like it, and you also have a chance to see a bit of Tesla history with some Roadsters and Alpha and Beta Model Ss.
Excellent write up by the OP about his experience at the tour and the delivery.
Congrats on getting your car for the holidays and sharing the joy with your family.
you wouldnt pay CA tax unless you registered it in CA.