Here's the website to check road conditions in Oregon:
http://www.tripcheck.com/RoadCond/roadcondindex.htm

And here's the one for California:
http://www.dot.ca.gov/hq/roadinfo/

You can also get good information to plan your travels at www.weather.com

Or you could go to this website this gives you links to highway conditions across the US and Canada:
http://www.highwayconditions.com/

Sorry that I have no information on shipping charges as I've never moved cross-country. I might suggest that you drive the Maxima instead of towing it. You could drive next to each other and communicate via FRS radios. I know when my brother-in-law and their family moved from Renton, WA, to Ft. Worth, TX, they did this. It made it nice because they got peace and quiet and took turns having the kids with them so no one got too stressed out during the trip. Just a thought.

Hope your move goes well.