Having just come down the northern California coast, I can give you some suggestions. Make sure you drive the Avenue of the Giants. This is a 31 mile stretch of the old routing of US-101 through Humboldt Redwoods State Park.

CA-1 from Leggett all the way down the coast is very winding and slow. To plan your time, calculate an average of 30 mph. It will take you at least 2 hours to get from Point Arena to Bodega Bay (60 miles or so). The best way to I-80 would be to go through Bodega Bay, and about 1 mile after going through Valley Ford, CA-1 makes a right turn. Don't turn, continue straight on Valley Ford Road, it will become Bodega Ave, take that into Petaluma and go south on the US-101 freeway. Take that to Novato and pick up CA-37 east to Vallejo and get on I-80.