Help Moving NAT from Public to Private IP Range

Hi

Currently we have Free PBX on a public network address 96.xx.xxx.xxx

for security we want to move the machine to a private address ( 10.0.0.xxx ) and NAT the 96.xx.xxx.xxx to the 10.0.0.xxx - all services to 96.xx.xxx.xxx will to mapped to a system on 10.0.0.xxx

Can anyone suggest what config changes are required, and where to make them, in Freepbx to accomplish this task?