HELP - Authenticating user from CRM (using API) in order to view "members-only" content on EE

Hi all. I must start by saying I’m a designer and not a developer. I’ve built many EE sites, but I have a requirement that I need to determine I can do “easily” with EE.

I have a client that is using a new CRM for various reason including event registrations, memberships, etc. They also currently have their EE-based website that has a members-only section in which everyone has the same login username and password.

They want to do things differently now. On the website, they want to display members-only information to members, with unique usernames and passwords, that are authenticated by the CRM. The idea is this

1. The logged-out member goes to members-only page on the website and they view the login form
2. They enter their username and password and it tests (via an API) that the user is and active person “member” in the CRM
3. If they pass the authentication they can view the members content and EE recognizes the session so that they don’t have to log in every time they visit another members-only page within that same session.

I hope this makes sense. Any suggestions on how I can accomplish this?