yes

Alaska is mainly C, D, and N gates. They are linked by a train line. The trains are in the N island ( must use train to access) far/ high end of C gates, and low numbers of D gates. If you transfer from N to D be careful because when you exit the train at D one way is the security exit to baggage claim . the other takes you above to D concourse.

your flight will probably change again. It’s generally stable once you are within 60 days of flight date.

Seattle is easy todo on a long layover. It’s about 25 min by cab/uber/Lyft but traffic dependent. 45 min by light rail to main downtown area a few blocks from Pike Place. Seattle airport has a baggage hold location in baggage claim area. Downtown area also has art museum and aquarium among other places. The Boeing museum is not easily accessible by light rail but it’s about half the drive time from the airport.

if you have a little longer layover. In the central area there is a small shopping mall and food court area inside security between the C/D/N and A/B/S. It runs between the C/D split and A/B split. Concourses have stuff. Alaska N gates is relatively new with a major redesign completed.