Enrolling a Learner with Webhooks and Zapier

I would like to use a webhook to enroll a learner into a course with a Zapier workflow.

A few problems I'm trying to work through using this methodology I hope others can provide some clarity or additional information on.

1. Since I have to pass the learner "ID" can that be obtained by another hook?  I know the UID or Email (they are one and the same for us) but not the Bridge generated ID, which is numerical.

2. If I have to create a learner, easy... how do I obtain the Learner ID after creation?

3. If I create a user using a hook, will I get a response that includes the ID that I can then use in a hook to enroll in the course?

4. If the user I am trying to create already exists, I'll get an error?  I don't see any method in the hooks documentation to "view" user info so I need to assume a user already exists if error... but how to get the ID?

Hoping someone can understand my process and provide some good suggestions.  Thanks.