Decomissioning/replacing media servers

My current environment consist of 8 media servers (4 at each site). Also an IBM tape library, DataDomain and NDMP hosts at each site.

The plan is to decomission 2 media servers from each site.

I'd like the remaining 4 media servers (2 per site) to take over the roles of the media servers being decomissioned.

I am aware of the nbdecommission utility, just not so sure about the actual steps for my type of environment.