I've done the in-place option, first upgrading the OS, then eDirectory,
then IDM, and it was just fine. I disabled eDirectory before starting (so
it would not turn on with reboots) and made sure that schema extended with
the 4.7 install (since that is necessary) and everything was fine. As
long as it's just engine/drivers, it should be fine. Be sure to apply new
activation codes (licenses) afterward, or eventually your drivers will
just stop turning on during a maintenance window reboot when you do not
expect it.

Good luck.

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