For workflows you can log in as the default commvault user in the java console, go to workflows, right click the workflow to change, select all tasks, select Take Ownership. Following on this activity you want to Deploy the workflow from the same menu to force the workflow to be executed by the default commvault user.
Regarding jobs I will have to look in my history, I have this solution in there somewhere :p
Edit: You can change the schedule owners and therefor the user performing the jobs with the following command line:
qoperation execscript -sn changeScheduleOwner -si @oldUserName -si @newUserName
Senior Technical Consultant