How to change System Account on SharePoint 2010

If you must change account System Account on SharePoint2010.
In my lab.
I want to change spsysadm(Old account) to spappadm(New Account) . The account spappadm is run all service on SharePoint.

Before configure create new account in active directory .

1. Add new account to administrators group local.

2. Add user to SQL Server on sysadmin roles.

3. Add user new account to farm administrators on central admin.

4. Register managed account for new account on central admin.

5. Change all service on old account to new account on register on (4)

6. Change account :
Application Pool on IIS : Change old account to new account on running services application pools.
Services Windows Server : Change old account to new account on this account current running services.