How can I find and replace all values without opening the plans?

You can find and replace using the Search option in the upper panel of DQC.

1. Click on Search and enter the text you would like to replace.
2. Click on Replace, and enter the new text you wish to use as a replacement.
3. Clicking on Preview will display a dialog showing where text was found, and a preview of the XML representation of the plans, before and after the change. You may want to uncheck some of the locations.
4. Click OK.