[kbs666]

What Vargr said.

Create a "master" realm that would be a copy of your existing realm. delete everything specific to the existing campaign leaving just the stuff that is specific to the world and game system.

Then you need the discipline to maintain 2 copies of the realm. The "master" where you do all world building, which you export from everyone time you make changes, and the "campaign" level one where you build adventures for the new campaign. This will let you do this again in the future.