What rights do the biological children have after parent passes away?

My father passed away 1 mo ago. My father's wife (not biological mother) recently discovered that her name is not on the deed to the house. They were married for about 30yrs. No will was left. So my brother and I are wondering what steps do we take. We would like to find out if he had any 401 k, bank accounts, etc. Also about the 3 vehicles he has.