D&U to E mode migration path

with the 10.13.x distro now officially out of the beta mode,

are there any pointers / hints / whatever, on how to migrate from currently configured D&U mode to Extensions ? Is it required to switch to Extensions mode before upgrade or can the upgrade process handle this (and how does it do that) ?
(as a ‘bonus’, I don’t use VM, so there is nothing to migrate there - all I use is queue(s) and the Asterisk Phonebook)

Thanks In Advance.