SeaTac (Seattle-Tacoma) airport is the one that serves the region. Lot's of flight options from all over the world.

If you can, the best way to get into the city center from the airport is the Light Rail or the LINK. There are signs throughout the airport that point you to where to catch that. It is limited to one line, so if you're staying further from a station, plan to uber from the station or take the bus. Taxi's are more reasonable than Ubers here, for the most part.

The party will be in Pioneer Square. The "cool" neighborhoods are Capital Hill and Ballard. Pioneer Square and Capital Hill have light rail stations. Ballard would require more finagling for transportation.

You can! But note, driving in Seattle is miserable. If you've got patience in spades, go for it. If you get annoyed by bad drivers, maybe shy away from renting a car.

That's up to you! The only thing of note is that the party is on a Friday. So make a long weekend of it or do the whole week. Check out the "Things to Do" tab for activities in and around Seattle.