I am 66 and retired. I would like to cash out my 401k. What can I espect to pay in taxes?

You will pay ordinary income tax on the withdrawal - assuming you have no after-tax portionin your 401(k). You can add the amount of the withdrawal to your expected income from other sources (wages, social security, investments, etc) to figure out what tax bracket it might put you in. If you live in a state that has income tax, you will have to pay that on the withdawal as well.