Good route, scenic and goes close to Jack London's home. I have driven it a number of times. You should do fine in that rig all the way. When you get to Sonoma, Find a parking place and tour the main part of town. I highly recommend cheese from the cheese factory and bread from the bakery on the square. Mary's Pizza Shack restaurants get their bread from this bakery.
From Napa to I-80 is no problem. From Susuin to Rio Vista needs watching. If it is real windy, that stretch takes the brunt of it, so be prepared.
Enjoy!