Changing default desktop back to Ubuntu after installing additional desktops

Hi,

I originally installed Ubuntu 10.10. However, I wanted to play with some
additional window managers, so executed:

sudo apt-get install xubuntu-desktop
sudo apt-get install kubuntu-desktop

Now, I like the choice I get on the login screen for the various window
managers (as well as three guest-restricted access selections!).

However, I'd like to change the login screen back to the Ubuntu look and
feel. I don't know if this is just a theme setting, or something more.
I launched the application System --> Administration --> Login Screen
Settings, but all choices on this screen are grayed out, and the Unlock
button doesn't do anything.

Finally, I'm getting a password dialog after logging into Ubuntu about
unlocking password keyring. Any way to get rid of this dialog?

Thanks,
Scott