Can I change a DLC price after publishing?

I'm working on a game with DLC. I'm trying to find out how much flexibility there is in setting prices and sales on the DLC.

1.
After publishing a game with DLC am I free to change the price of the DLC? If so can I do this through the dashboard or do I need to email store support? Any restrictions on this?

2.
Is there a way to put DLC's on sale? Or is the only way to be invited into a sale?