Configuration Wizard - Setting up the WAN info - inside or outside interface?
I'm kind of confused here. It is asking in the Gen Config section for the MAC address, MTU and MSS. Now for what device is this? My modem is a router/modem and it has 2 mac addresses a WAN and LAN address. It also has a LAN and WAN IP address, the LAN is the address I use to access the device (192.168.254.254) and the WAN is the outside address from the ISP.
So am I correct that I would use the LAN address here for the WAN configuration in pfsense or does it really want the interface that is facing the outside traffic?
That whole screen is for the WAN settings. At the top it says "On this screen we will configure the Wide Area Network information".
For 99.9% of installs MAC Address, MTU and MSS are left blank - you should leave them blank unless you have some really special reason to need a magic value.
For now, if you are leaving your front-end router/modem in its modem+routing mode, then you can leave Selected Type as "DHCP". It will be given a private address and default gateway from the front-end device that is in "front-end LAN = pfSense WAN" and use that to get out to the internet. It will be just as if the whole pfSense box, and the "pfSense LAN" behind it are 1 client on the front-end LAN. In this configuration the pfSense LAN will NAT onto front-end LAN, then front-end LAN is NATed out to the real internet.
At a later stage you can put your modem/router into bridge mode (so it stops doing "router") and passes the real public IP through to pfSense WAN.