Some advice

Don't eat yellow snow..........believe me, it's useful advice ;)

In all seriousness, I think people might be having a hard time giving you decent advice since you're not particularly clear on what kind of advice you need. 

On the assumption that you will have arrived in Bilbao by ferry and have a car - it's about a 9 hour drive, so doable in a day. 

If you use www.viamichelin.com then this can provide routes that avoid toll roads and, if you input your car details, even estimate your fuel consumption and cost!

Hope this helps!