How do I change all caps to lowercase?

Highlight all the text you want to change. Hold down the Shift and press F3 . When you hold Shift and press F3, the text toggles from sentence case (first letter uppercase and the rest lowercase), to all uppercase (all capital letters), and then all lowercase.

How do I change caps to lowercase without retyping?

Select the text you want to change the case of, using your mouse or keyboard. On the Home tab of the Ribbon, go to the Fonts command group and click the arrow next to the Change Case button.