It isn’t really safer.
If the new server fails to build/install correctly, just down it (or rename & re-address it) and bring the original back up.
If you do go for a parallel install, you just need to upload a copy of the new masthead on the old server and have a task to copy it to clients and restart the BESClient service.
Read the documentation, search through this forum for helpful threads and practice on a test system.
And you can raise a pre-emptive case with HCL to explain what you are doing and there will be support available while you do the work.