Hi,
personally I would try:
- backup my whole system with a snapshot/dd, what you want (to be able to come back to a working ststem very quickly)
- backup yunohost
- erase all and re-install 64 bits version of your OS
- re-install yunohost
- finish post-installation by restoring your yunohost backup.
I did it one time without issue, so it should be fine, but I think it’s also dependant of the installed apps on your system.