Seperation of application specific view/controller stuff

I installed both login and user engines and got them working. Thanks for
an excellent job! Now, I have some questions on how to customize them
without breaking the code or making future upgrades messy. I have
several questions and any help will be greatly appreciated. I am
designing a student registration app for a community college.

First the view stuff. I’d like the signup/login/logout/change password
to be available via a sidebar. Basically I am trying to make this app
feel like a desktop all using Ajax.

I would like to have a lot more fields in the user table for the user
(student) profile and preferably I’d like to put the edit form right in
the side bar using an Ajax call. I currently have my cart for courses
chosen in the side bar and I’d like the whole login system to work in a
similar fashion. For example can I make a link_to_remote Ajax call to
:controller => user :action => signup and have it replace a div inside
my sidebar? How would I create a partial for that? If the rhtml files
are in my app/views will the engine know how to find it or is there a
configuration option for it?

Next the controller stuff, it says in the UserController to overide the
home action. I’d like the home to be Catalog/welcome. How do I overide
this?

With regard to the user_engine, I’d like students to be able to self
register and access their own records (both profiles and course
selections). The college staff can access ALL registrations and also the
courses database. So the admin creates staff users with these
permissions. I don’t need the guest role and the user role. Admin will
define a student role for the self registration. Can I delete the
default user and guest roles? How do I make registering students
automatically be assigned this role?

Thank you in advance,

bakki kudva