Customer login database, email, and payment

I’m hoping to integrate paypal, a broadcast email service, and a client database login feature to achieve the following:

1. Client comes to my sight and registers. The user’s information is stored in a database
2. Client returns to the site later and purchases something. The clients purchase is automatically registered and viewable in the database.
3. Client returns to sight later to see what they purchased and is able to login to view their specific purchase.

I’m having a hard time figuring out how the login feature integrates in this situation. Can the above example be achieved using one, or a combination, of plug-ins? Thanks in advance for your help!