Change logon account for MSSQLSERVER on SQL server 2008 r2

Hello,

The SQL Server 2008 R2 is running on Server 2008 R2 and is not clustered. MSSQLSERVER service is running with Network Service account. The server is in production and has multiple database and data warehouse.

What is that best way and any issue associated with changing the account on MSSQLSERVER service  from Network Service to a domain account that has a password which never expires.

Thanks