Problem with apt-get after enabling unstable tree

[Kaspar Fischer <fischerk@inf.ethz.ch>]

Hi everybody,

I have a very basic problem and would be glad to be pointed into
the right direction: Some time ago, I installed debian-sarge and
was forced to install a version of samba that was only available
in the unstable tree. Now that an updated version is already
available in the stable tree, I would like to

- uninstall all packages from the unstable tree
  (Notice that the original install of samba from the unstable tree
  required installation of OTHER packages from the unstable tree.)
- remove the unstable tree entry from /etc/apt/sources.list
- install samba anew (but from the stable tree)

How can I do this, i.e., tell apt-get to uninstall everything
from unstable and install "the same" packages from the stable
tree? I currently end up having tons of dependency/etc. problems.

Alternatively, I am willing to reinstall from scratch, but again
do not know how to do this. Can I tell apt-get to uninstall all
but the most basic packages? Then I could manually reinstall
what I really need.

Thanks a lot for your help,
Kaspar