Do you need Static IPs for Dual-WAN Failover? / Can't get failover working

Do you need to have static IP addresses for Dual-WAN Failover?  Or just for Dual-WAN Load Balancing?

I have two WAN connections from two different ISPs and I want to set up one as a backup (failover) connection.  Can both of these WAN connections be DHCP?  Also, I have port forwarding set up with the main WAN interface selected.  Is it possible to switch the port forwading WAN interface to whichever interface is the active WAN connection?

Is there an example config to set this up without running through the wizard? (I don't want to lose all the config I currently have set up).

From what I found on the web, I added the config pasted below to set up dual WAN failover with primary on eth0 and backup on eth1.  I'm confused what Group "G" means?  Also, once I added the following config, when both WAN connections are up, the internet doesn't work.  If I disconnect the primary WAN, the internet works.

Thanks!

ubnt@ubnt# show interfaces ethernet eth0
address dhcp
description "WAN 1"
duplex auto
firewall {
    in {
        name WAN_IN
    }
    local {
        name WAN_LOCAL
    }
}
poe {
    output off
}
speed auto

ubnt@ubnt# show interfaces ethernet eth1
address dhcp
description "WAN 2"
duplex auto
firewall {
    in {
        name WAN_IN
    }
    local {
        name WAN_LOCAL
    }
}
poe {
    output off
}
speed auto

ubnt@ubnt# show load-balance
group G {
    interface eth0 {
    }
    interface eth1 {
        failover-only
    }
}

ubnt@ubnt# show service nat
rule 5000 {
    outbound-interface eth0
    type masquerade
}
rule 5002 {
    outbound-interface eth1
    type masquerade
}