anyone have a simple way to switch my wan interface to port 5 on a hap ac lite version 6.43.8? new interface list is confusing me as I'm just learning this OS.
It depends on whether other end of your ether5 will have dhcp-server on it. If yes, then:
/ip dhcp-client add interface=ether5
// To add the interface as DHCP-Client, by default it will add peer DNS advertisements and add default-route to your configuration.
Now edit/check your NAT settings to be sure that your LAN traffic is forwarded correctly.
Other changes will depend on your current settings, so if you still have problems, post the configuration.