Unfortunately that is not very intuitively done in Skype. What you need to do (and this is for all extras the same), is open Skype and click on the "Tools" menu, then the "Do More" menu. Click on "Organize my Extras".

The Skype Extras Manager window will open. Click on "My Extras" (if not selected already). You will then see one or more entries there with the green play button. Next to it you will see a grey button called "Menu".

Click on that and select "Uninstall". This will uninstall the application. Note that the Pamela data directory will not be removed, so you will still have access to your call recordings made with PCR.

If you want to install the freeware Pamela Basic or try one of the other versions you can now do that. Open the Pamela download page and download and install the version you want.