The easiest way is to log into SQL Server with the desired account and change the name of the maintenance plan, and then change it back. Open each sub-plan and re-save to update the jobs with the new owner.
You may need to also make a change on at least one task to force an update of the job, but I have found that most of the time that is not needed.
Another option is to update the table directly, but that is a bit more difficult.
Jeffrey Williams
“We are all faced with a series of great opportunities brilliantly disguised as impossible situations.”
― Charles R. Swindoll
How to post questions to get better answers faster
Managing Transaction Logs