Well I'm still unclear as to what it is you don't want to loose. There is a big difference between running config and startup config. If you can copy run to start before you do anything else, you can avoid loosing your running config (because it will become your startup config). Even then, you just need to be cautious. I think you have it right. Make sure that you copy your start to run, make your password changes, and then copy run back to start. Nothing lost.
If you can't copy run to start before beginning the procedure, you are going to end up reverting to whatever the startup config is. It may be the same, it may not.
Hope that makes sense.