Changing third-party administrators (TPAs) isn’t fun. If you have to for it, do it. However, you need to coordinate with the new TPA with the entire conversion process. TPAs are greater experts at the conversion process than you are, so let them run it.
This isn’t the time for you to go into business for yourself and run the process without the new TPA’s knowledge and advice.
You hire pros, let the pros run the process.