How Can I Prevent User Updates

[across]

Hello,
We are implementing single sign on to our forums via our dealer portal. To do this, we are exporting user id's and passwords from our portal and hardmapping them to our forums. As such, we wish to prevent password changes. I found some posts regarding this, but the information given was limited. I have no idea how to remove the editable fields nor all the templates that might be involved. I know it is a lot to ask, but if someone could take the time to tell me how to do this and which templates I'll need to change, I'd greatly appreciate it.
Thank you,
Angela