What do you mean by other devices?
You can simply remove the old MX and add the new one to the current Network, as long as you do it within a maintenance window.
Removing the MX will not cause you to lose your settings.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
Please, if this post was useful, leave your kudos and mark it as solved.