Hi,
It is always good practice before revoking DBO role,identify what user has the permission on database level &it's Objects.
Once in Handy ->You can perform through the GUI i,e if that user has any dependency permission -then remove first then go with the revoking DBO
or
best way use the T-SQL commands.
Note ->Just for information only-
Identify that what are all the Jobs(applications/Maintenance Plan jobs) are depends on those Id's? Because you are going to revoke High Privilege role.
If you are Ok to revoke role then you can ignore.
Regards,
Rama Udaya.K