Setting up Mp70 for failover


I have read this failover article Configuring WAN Failover with a Cisco 881 Router and an AirLink ES440

But unsure if it applies to my situation.
What I want to achieve should be simple.
If the ethernet connection from the mp70 fails to see the network or internet; fail over to the cell.

Also I want the mp70 to have a static IP on the network, so I set that and restarted it, but it loses it upon reboot and I have to reset it to get back to the web page to manage it.
Any help would be greatly appreciated.