Ninja Form Data copy from/to Vendor Custom Fields


I have a Ninja Form to collect registrations for an upcoming Harvest Market single date event.

Some or Most of the users registering will already be 'vendors' (custom post-type 'vendor' done with Custom Press)
I plan on tying 'users' (capability role: vendor) to their own 'vendor' page.

My question is this: Can I or what is the best way to approach sharing common field values such as First Name, Last Name, Address etc between 'vendor' custom fields and Ninja Forms submissions.

In my dream scenario, if user is logged in and visiting the registration form, the data from his vendor profile post would auto-fill on page load. He would still be able to edit the loaded values. (Perhaps the changes made on registration form would replicate to the vendor profile as well but not necessarily, I haven't decided)

Thank you