Been a couple of years but I'll give it a shot.
They do allow overnight parking and it seems up to a week stay. No charge when we were there. Fairly large parking area no hookups or dump station then. There are signs to the parking area to the rear of casino. Had a phone number you could call and security would come out and register you. They seem to watch parking very closely. They didn't allow truck parking on premises so you will not have that noise and coming/going problem.
Beautiful casino and grounds. Food was mediocre. For us the free parking was anything but, hope your luck is better.
Another option in the area is Angel of the Winds off of exit 210. Smaller but great staff and food. They have electric and water(?) hookups. I think they have added a dump station. Has fuel station. They charge $15 (?) night but do take reservations..
Jealous about the Boeing visit. Used to deliver freight there years ago, that place is huge.