MN to Oakland
 

I am looking for advice on driving from Saint Paul, MN to Oakland CA in June. Is there a way to avoid mountain driving or long tunnels? Timeliness is somewhat important but we want to avoid difficult roads. Google suggests either I-80 straight across, I-90 to I-80 or I-94 through NO. Dakota, Montana and Idaho. But I can;t seem to get an idea of terrain and steepness of roads. Help!

You can't get to California w/o going through mountains . . . unless you go waaaaay south and across to Southern CA and up the Central Valley or 101.

If you don't want to drive through mountains, you'll need to fly.

If you can handle driving in the Twin Cities, there shouldn't be anything for this drive that should worry you. Take the 35 to the 80, its so easy it will bore you. I haven't done 90, but 80 and 70 are no problem.

btw- You should be going through Des Moines during lunch, go to Wasabi Tao, best quality Sashimi Lunch Specials in the country

Interstates are designed to standards that will make it quite easy for you. Here they are.

"Maximum grade: Maximum grade is determined by a design table based on terrain and design speeds,[1] with up to 6% generally allowed in mountainous areas and hilly urban areas with exceptions for up to 7% grades on mountainous roads with speed limits below 60 mph (95 km/h)."

So take the fastest route.

If you don't need your car in Oakland, you can take the Amtrak Empire Builder to Portland Oregon and then the Coast Starlight south to Oakland Jack London station.
This would involve about 62 hours on 2 trains with a 4 hour layover in Portland.
Portland has several good places for lunch before getting on the Coast Starlight at about 2:15PM.
The Empire Builder leaves MSP about 10:25 every night.
The recent timekeeping has improved greatly. At least 3 days last week the train arrived in Portland 10 to 20 minutes early.