in our environment we have a Smart-1 25 appliance with a R71 IPSO and a six months data logs repository. The Smart-1 manage 2 VRRP-Cluster Nokia-IP appliance gateways. Our purpose is to upgrade the old Nokia-Ip with a new hardware and migrate the Smart-1 25 appliance to the R75 GAIA platform maintaining the logs and the current configuration.
What is the best and fast approach to reach this scope? How long does it take to upgrade to R75?

Thanks in advance.