Just stop by and visit, they are open daily.
Boeing Field is closer to SeaTac. I assume you mean, Paine Field in Everett where Boeing manufactures the 747, 787 and parts of other programs, they do provide a factory tour. You should contact them directly in advance to get the specifics. There is a flight museum at Paine Field, but the big flight museum in the area is located at Boeing Field which is south of downtown Seattle and north of Seattle Tacoma International (commonly referred to as SeaTac).
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