questions re updating to -CURRENT

Hello:
	I finally get to update a system from:

FreeBSD 11.0-RC2 #0 r304729: Wed Aug 24 06:59:03 UTC 2016 amd64

	to -CURRENT.
	After reading src/UPDATING, I understand everything (I think)
_except_:

20170311:
	The old drm (sys/dev/drm/) drivers for i915 and radeon have been
	removed as the userland we provide cannot use them. The KMS version
	(sys/dev/drm2) supports the same hardware.

	I assume the new kernel bits will be automatically built and
installed.  Are there any changes I need to make elsewhere,
e.g. loader,conf or ports?

	Also:  as part of the "safest in-place upgrade" ... how do

	rm -rf /usr/obj/*

	and

	make cleanworld

	differ?



			Respectfully,


				Robert Huff