Creating Users Accounts, storing data, etc

Hello All,
I am in the planning stages for a client who needs some specific features on their website, and I am curious as to the best way to accommodate this.

The requested features are:

— A secure way for users to create personal accounts that store their information and tracks their history on the site

— High security forms that takes users through ‘stages’

My questions is: What is the best way to accomplish integrating these features into the site- is there a service that works with WordPress, or is there plugins for these features?

Thanks in advance!
– j