Removing user/pass login and adding a custom one

[gnosisprod]

I've integrated a membership system (Amember) with vbulletin3. When this happens all of the registration is done in Amember since Amember is integrated with vbulletin. When a user is logged out, the username and password (login field) is displayed at the top right. I'd like to have it look EXACTLY the same, but add a custom login. What I mean is simply that it would log you in through Amember and not vbulletin. Amember provides the appropriate user/pass login field code for php so this shouldn't be too hard. Where can I find where to edit that, and exactly which code would I replace?


PS: as a side note, after a user is logged in it says something like

Welcome, USERNAME.
You last visited: Today at 02:09 AM
Private Messages: Unread 0, Total 0.

It would be great to display a custom field below that for registered users which would be a 'time left' field (time left on their paid subscription). I think I'd probably have to get code from Amember to do that but for future reference where would I look to add something like that?