In R81 and above, we actually hide the traditional Geo Policy settings if nothing is configured there.
This is documented here: https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solut...
There are still parts of MAB that require SmartDashboard even if you move away from the Legacy mode.
In terms of upgrading in place, I would consider doing an Advanced Upgrade for your management (at least) so you can leverage the faster XFS filesystem (versus ext3).
That requires new partitioning and thus can't be done in place.
From R80.20, upgrading to R81.10 should be a single-step upgrade.