Creating addon that pulls dropdown selections from external api

I am learning how to use the gravity forms add-on framework and am having difficulty figuring out how to create the following:

  1. User selects New or Existing Patient
  2. go get list of options from external api, populate the next field dropdown options and then display it
  3. upon selecting from dropdown list display “Next” button (multi part form)
  4. go get list of avail dates and times from external appointment availablity api
  5. Create visual calendar (custom field) that upon selecting a date opens up and shows available appt times
  6. User selects appt time and “Next/Previous” buttons show up
  7. If user selects “Previous” the values selected so far are maintained and populated when the user sees the form . Same for “Next”
  8. User then fills out additional field data
  9. Any validation errors throughout maintain selections, including opening up calendar date and highlighting the selected appointment time.

I have gotten parts of this working, but am hoping some one can point me to:

  • Tutorial that would be helpful
  • Hooks that would be used in this
  • Tutorial on how to use the javascript hooks (I have used the php hooks already)
  • a sample add-on that would be good to look at.