Thank you! This is a huge help. I am posting the little script I wrote (for SQL2005) for anyone's additional reference.

--To view all the packages and their owners.

SELECT dts.name AS package_name

,SUSER_SNAME(dts.ownersid) AS package_owner

FROMmsdb.dbo.sysdtspackages90 dts

ORDER BY package_name

--To view all the info on the maintenance plans

SELECT*

FROMmsdb.dbo.sysdtspackages90

WHEREpackagetype = 6

--Find out the OwnersId for the login you want to use.

SELECTloginname, sid

FROMsyslogins

--To Update the owner

UPDATE msdb.dbo.sysdtspackages90 SET

ownersid = 0x0105000000000005150000000421C9C7B2AB5D056CCD5020D82A0000--Copy/Pasted from above script

--WHEREname = 'UserBackup'--Change a specific SSIS package

WHEREpackagetype = 6--To change all maintenance plans