Yes, 100% you would lose access @tommyV , because it would be brand new install from scratch, so it would wipe out all the settings once rebooted. Just curious, what sort of appliance is it? If you think about it, lets take most simple example, it would be like factory resetting say basic Linksys wireless router people use at home, it would wipe out all the settings and you would have to configure it from scratch.
You can verify if it qualifies for the upgrade below:
https://supportcenter.us.checkpoint.com/supportcenter/portal?eventSubmit_doShowupgradewizard
Happy to do remote and we can check it together.
Cheers mate.
Andy