Do you mean RCM and the Revenue Cycle Model and Lead Lifecycle?
Marketo usually suggests editing the model, but if the changes are dramatic, I'd say build a new draft model, then plan out the new RCM and LLC campaigns in a separate program. In fact, I'd do a draft new model and then decide if I could edit the original RCM and values to retain the historical data.
But if you do either option, some of your data will be cleared out and your reports will essentially start over. You will also need to rebuild some reports if you completely rebuild the system.
Edit a model:
https://community.marketo.com/MarketoTutorial?id=kA250000000KzWoCAK&refURL=https%3A%2F%2Fcommunity.marketo.com%2FMarketoDeepDive%3Fid%3DkA5500000008QOkCAM