Before installing OpenRC, the /etc/init.d folder would need to be moved out, ie:
# mv /etc/init.d /etc/init.d.bak

After installing, /etc/inittab would need to be replaced. The old one can be backed up:
# cp /etc/inittab /etc/inittab.sysvinit
# mv /etc/inittab.new /etc/inittab

Services for OpenRC can be found in the openrc-services package.