from hardware appliance to virtual appliance

a big customer has to make this transition: from hardware appliances to virtual appliances. What is the best practice for proceeding? Is it necessary to change the IP adress of the new virtual appliances? Is it possible to upload a backup created from the hardware appliance (primary node) and install it on all the virtual appliances? (without loosing nothing)

Can you please give me all helpful and useful information about this change?