Hello SonnyN1,
After upgrade to Parallels Desktop 8 or 9 you cannot change the Release Input shortcut in Parallels Desktop ->Preferences as the function is greyed out.
In order to assign different shortcut for Release Input function, please open System Preferences on Mac -> Keyboard -> Shortcuts -> App Shortcuts -> Parallels Desktop and add a new string for Release Input:
If Parallels Desktop is not present in the list just click on '+' button and chose Parallels Desktop in the Application drop-down list.