One of the useful tools for an upgrade situation is the Catalog Preview
tool. It requires Puppet 3.8, which should be a much smaller jump for you
(3.7 -> 3.8) to begin with. It'll probably help soothe worries for the ops
team by allowing a level of testing and certainty before the big jump.
Been through a similar upgrade myself. The first step would be to spin up
a new puppet master running Puppet Server. You can copy over the SSL dir
from your old/current master to avoid SSL errors on the agents. For
testing you'll want to make sure your manifests work correctly using the
