Replace a 2002 Explorer heater.

I am installing a Mojave heater in my 2002 Ford Explorer [it costs $1000 to have dealer replace the $15 stripped plastic thingy under the dash]. I simply want to know how to identify the in and out hoses at the firewall under the hood. For what its worth, they have ID and OD printed on them. ALSO, will the water flow through the Mojave heater once the hoses are reconnected to it w/o any further action. I have just made a small donation.