We've built our NBU masters on identical hardware just for this reason. If we needed to, we could image the original NBU master (we make these periodically) and restore it to the (in your case) NBU media server & be up and running quickly.
If you run EMM on the NBU master like we do, changing the NBU master may not be enough. EMM holds all the data of who wrote what where when, etc.
We can restore the EMM data to get the catalog up to date from there.