Upload & Sell: Off
I'm about 4 hours away and have made the trip in all seasons many times - from blizzards to mid-summer heat. You really can't go wrong any time of the year.
As for the most common vantage point for sunrise / sunset it is likely to be Steptoe Butte. From there you can get a 360 degree view, unlike Kamiak Butte.
There are countless small dirt roads throughout the region that are open from March 15 - November 15. If it hasn't been raining (the clay can be treacherous), explore, explore, explore. That's the joy of the Palouse. Sure, we all have some special spots that we return to but what "floats my boat" may not float yours.
I have, on many occasions, just pulled over on one of the back roads through the hills and slept in my vehicle. If you'd prefer a motel, I can recommend the Best Western in Colfax. I've stayed there quite a few times and it is clean, comfortable, and very centrally-located.
Could I get a good feel for the area in one night and two days?
Yes, but it will only whet your appetite since there are so many back roads to explore. I would also suggest a side trip to Palouse Falls State Park, perhaps on your return leg since it is a bit out-of-the-way. It is quite photogenic.