you could try either... the key is that you'll need to move BOTH interfaces to something free...
this may be tricky... as applying these settings may lock you out... best to copy/backup the /etc/config/network original... ( preferrably on a pc that can mount ext4 )
then switch the ifnames for wan and lan to whatever the new names are... ( eth0 > nic0, eth1 > nic1 )... then reboot and cross your fingers...
any other references in your config will need to be altered too... ( /etc/config/luci_statistics?, /etc/config/sqm? etc. etc.)
nope... that's pretty much correct...
just macmatch and ifname (new ifname)@/etc/config/network>interface/s