burn some nice rock music to keep u awake... you dont need GPS for this trip...when u get close to seattle maybe yah u might need...  just straight long boring drive.. specially if u are driving alone.

pack some sandwich, snacks...

when tank is almost empty, stop by gas station, get coffee, caffeine drink to keep awake.

North dakota is dead area so u will be bored as hell driving thru that area.
once u get on to montana, the scenery can be nice.. maybe take some pictures around montana if u are there during day time, they got great views from there.

i think the biggest cities on your way is sioux falls, sd, fargo, nd and spokane, WA before getting to seattle.

good luck... safe driving...