Upgrading SQL Server 2008 Instances with replication to SP3

I have three servers SQL Servers involved in replication.  

• The publisher is SQL ENT. 2008 SP2.  
• The distributor is SQL ENT. 2008 SP2.  
• The subscriber, (also a publisher) is SQL 2008 Ent. SP3.
• Hundreds of publications are invloved.

I want to upgrade the publisher and distributor to SP3.

Is there any specific order that the upgrade should be done ?

Are there any specific recommendations for upgrading servers involved in replicaton ?

Thanks Steve B.